U.S. patent application number 12/670373 was filed with the patent office on 2010-09-09 for enhanced biodegradation of non-aqueous phase liquids using surfactant enhanced in-situ chemical oxidation.
This patent application is currently assigned to VERUTEK TECHNOLOGIES, INC.. Invention is credited to John Collins, George E. Hoag.
Application Number | 20100227381 12/670373 |
Document ID | / |
Family ID | 40282032 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100227381 |
Kind Code |
A1 |
Hoag; George E. ; et
al. |
September 9, 2010 |
ENHANCED BIODEGRADATION OF NON-AQUEOUS PHASE LIQUIDS USING
SURFACTANT ENHANCED IN-SITU CHEMICAL OXIDATION
Abstract
A method for in-situ reduction of contaminants in soil that uses
chemical oxidation and biodegradation.
Inventors: |
Hoag; George E.; (Storrs,
CT) ; Collins; John; (Amston, CT) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Assignee: |
VERUTEK TECHNOLOGIES, INC.
Bloomfield
CT
|
Family ID: |
40282032 |
Appl. No.: |
12/670373 |
Filed: |
July 23, 2008 |
PCT Filed: |
July 23, 2008 |
PCT NO: |
PCT/US08/08905 |
371 Date: |
January 22, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60935033 |
Jul 23, 2007 |
|
|
|
Current U.S.
Class: |
435/262.5 ;
210/170.07; 210/610; 210/614; 210/620; 210/630; 210/631; 210/96.1;
436/183 |
Current CPC
Class: |
B09C 1/08 20130101; B09C
1/00 20130101; Y02W 10/40 20150501; C02F 2103/06 20130101; Y02W
10/45 20150501; C02F 2101/36 20130101; B09C 1/02 20130101; B09C
1/10 20130101 |
Class at
Publication: |
435/262.5 ;
210/631; 210/630; 210/620; 210/610; 210/170.07; 210/96.1; 210/614;
436/183 |
International
Class: |
A62D 3/02 20070101
A62D003/02; C02F 1/72 20060101 C02F001/72; C02F 1/70 20060101
C02F001/70; C02F 3/30 20060101 C02F003/30; B09C 1/08 20060101
B09C001/08; B09C 1/10 20060101 B09C001/10; G01N 33/24 20060101
G01N033/24 |
Claims
1. A method for reducing the concentration of a contaminant in a
subsurface to a predetermined level, comprising: introducing a
primary oxidant and a surfactant and/or a cosolvent into the
subsurface; the surfactant solubilizing or desorbing the
contaminant; the primary oxidant oxidizing the solubilized
contaminant in the subsurface to a biodegradable compound; and a
microorganism in the subsurface biodegrading the biodegradable
compound, so that the concentration of the contaminant in the
subsurface is reduced to the predetermined level.
2. (canceled)
3. The method of claim 1, further comprising: monitoring the
subsurface for a quantity selected from the group consisting of
contaminant concentration, oxidant concentration, surfactant
concentration, cosolvent concentration, microorganism
concentration, and combinations; and adjusting the amount of
oxidant, surfactant, and/or cosolvent introduced into the
subsurface to minimize the amount of contaminant in the
subsurface.
4. The method of claim 1, wherein the primary oxidant establishes
an oxidative zone in the subsurface in the vicinity of the locus of
introduction of the primary oxidant, wherein aerobic microorganisms
proliferate in the oxidative zone and biodegrade the biodegradable
compound and/or the contaminant, wherein oxidation of the
solubilized contaminant and/or biodegradation of the biodegradable
compound by the microorganism consumes the primary oxidant and
establishes a reductive zone in the subsurface surrounding the
oxidative zone, wherein anaerobic microorganisms proliferate in the
reductive zone and biodegrade the biodegradable compound and/or the
contaminant.
5. The method of claim 4, further comprising introducing a
secondary oxidant in the subsurface in the oxidative zone and
downgradient of the locus of introduction of the primary oxidant,
wherein the oxidative zone extends downgradient from the locus of
introduction of the primary oxidant, wherein the reductive zone
extends farther downgradient from the locus of introduction of the
primary oxidant than does the oxidative zone and wherein
introducing the secondary oxidant stimulates the proliferation of,
the metabolism of, and/or the biodegradation of the biodegradable
compound and/or the contaminant by the aerobic microorganisms.
6. (canceled)
7. The method of claim 4, further comprising introducing a
reductant in the subsurface downgradient of the locus of
introduction of the primary oxidant, wherein introducing the
reductant stimulates the proliferation of, the metabolism of,
and/or the biodegradation of the biodegradable compound and/or the
contaminant by the anaerobic microorganisms, wherein the reductant
induces a reductive potential in the reductive zone by reacting
with oxygen in the subsurface.
8. (canceled)
9. The method of claim 4, further comprising introducing a
reductant in the subsurface downgradient of the locus of
introduction of the primary oxidant, wherein introducing the
reductant stimulates the proliferation of, the metabolism of,
and/or the biodegradation of the biodegradable compound and/or the
contaminant by the anaerobic microorganisms and wherein the
reductant induces a reductive potential in the reductive zone by
acting as a food source for aerobic microorganisms and thereby
stimulates the consumption of oxygen in the subsurface by the
aerobic microorganisms.
10.-11. (canceled)
12. The method of claim 1, further comprising pumping contaminant
out of an extraction well to establish an extraction zone in the
subsurface.
13. (canceled)
14. The method of claim 1, wherein the overall rate of oxidization
of the contaminant is controlled to a predetermined value and the
overall rate of solubilization of the contaminant is controlled to
a predetermined value by selecting the primary oxidant and
surfactant and adjusting the concentration of primary oxidants and
surfactants, so that the rate of oxidation of the contaminant is
greater than, less than, or equal to the rate of solubilization of
the contaminant in accordance with a predetermined decision.
15.-16. (canceled)
17. The method of claim 1, further comprising introducing a
microorganism into the subsurface downgradient of the point where
the oxidant, surfactant, and/or cosolvent is introduced.
18. (canceled)
19. The method of claim 1, wherein the microorganism is an aerobic
microorganism and wherein proliferation of the microorganism is
stimulated by inducing an oxidative subsurface environment by
introducing the primary oxidant.
20.-21. (canceled)
22. The method of claim 1, wherein the microorganism is an
anaerobic microorganism and wherein proliferation of the
microorganism is stimulated by inducing a reductive subsurface
environment by limiting the amount of primary oxidant introduced,
introducing a substance that reacts with oxygen, or introducing
food for microorganisms.
23. The method of claim 22, wherein the substance that reacts with
oxygen is selected from the group consisting of a zero-valent
metal, zero-valent iron, zero-valent manganese, zero-valent cobalt,
zero-valent palladium, zero-valent silver, and a particle of a
zero-valent metal coated with a polymer and wherein the polymer is
selected from the group consisting of xanthan polysaccharide,
polyglucomannan polysaccharide, emulsan, an alginate biopolymer,
hydroxypropyl methylcellulose, carboxy-methyl cellulose, ethyl
cellulose, chitin, chitosan, polymethyl methacrylate, polystyrene,
and polyurethane.
24.-25. (canceled)
26. The method of claim 1, further comprising introducing a
nutrient into the subsurface, wherein the nutrient is selected from
a carbon source, a phosphorous source, a nitrogen source, a sulfur
source, a potassium source, a sodium source, an iron source, and a
magnesium source.
27. The method of claim 1, further comprising introducing a
nutrient into the subsurface, wherein the nutrient promotes
proliferation of aerobic microorganisms and biodegradation of the
biodegradable compound.
28. The method of claim 1, further comprising introducing a
nutrient into the subsurface, wherein the nutrient promotes
proliferation of anaerobic microorganisms and biodegradation of the
biodegradable compound.
29. (canceled)
30. The method of claim 1, wherein the primary oxidant is selected
from the group consisting of potassium persulfate, ammonium
persulfate, and potassium permanganate.
31. The method of claim 1, wherein the surfactant and/or cosolvent
comprises VeruSOL surfactant.
32. (canceled)
33. The method of claim 1, wherein the surfactant and/or cosolvent
is selected from the group consisting of a carboxylate ester, a
plant-based ester, a terpene, a citrus-derived terpene, limonene,
d-limonene, castor oil, cocoa oil, cocoa butter.sub.s coconut oil,
soy oil, tallow oil, cotton seed oil, a naturally occurring plant
oil, a plant extract, a nonionic surfactant, ethoxylated soybean
oil, ethoxylated castor oil, ethoxylated coconut fatty acid,
amidified, ethoxylated coconut fatty acid, and combinations.
34.-35. (canceled)
36. The method of claim 1, wherein the surfactant and/or cosolvent
is selected from the group consisting of ALFOTERRA 123-8S,
ALFOTERRA 145-8S, ALFOTERRA L167-7S, ETHOX HCO-5, ETHOX HCO-25,
ETHOX CO-40, ETHOX ML-5, ETHAL LA-4, AG-6202, AG-6206, ETHOX CO-36,
ETHOX CO-81, ETHOX CO-25, ETHOX TO-16, ETHSORBOX L-20, ETHOX MO-14,
S-MAZ 80K, T-MAZ 60 K 60, TERGITOL L-64, DOWFAX 8390, ALFOTERRA
L167-4S, ALFOTERRA L123-4S, ALFOTERRA L145-4S.
37. (canceled)
38. The method of claim 1, further comprising introducing an
activator into the subsurface, wherein the activator is selected
from the group consisting of a metal activator, a chelated metal
activator, a chelated iron activator, Fe(II)-EDTA, Fe(III)-EDTA,
Fe(II)-citric acid, Fe(III)-citric acid, and Fe-NTA.
39. (canceled)
40. The method of claim 38, wherein the activator has the form of a
particle coated with a polymer selected from the group consisting
of xanthan polysaccharide, polyglucomannan polysaccharide, emulsan,
an alginate biopolymer, hydroxypropyl methylcellulose,
carboxy-methyl cellulose, ethyl cellulose, chitin, chitosan,
polymethyl methacrylate, polystyrene, and polyurethane, wherein the
polymer coating is sufficiently thick for the activator to remain
capable of activating an oxidant in a location in need of
remediation for at least as long as an oxidant capable of oxidizing
contaminant in the location remains in the location and wherein the
polymer coating is permeable to an atomic or molecular species
selected from the group consisting of persulfate, sulfate,
peroxide, hydroperoxide, oxygen, and hydroxyl.
41.-42. (canceled)
43. The method of claim 40, wherein the activator particle travels
with the primary oxidant.
44. The method of claim 1, further comprising introducing an
antioxidant into the subsurface.
45. The method of claim 1, wherein an oxidizing environment is
established in a region of the subsurface around where the primary
oxidant is introduced and wherein a reducing environment is
established in a region downgradient of the oxidizing environment
and/or surrounding the oxidizing environment.
46. The method of claim 1, further comprising introducing a
compound that reacts with oxygen or introducing food for
microorganisms into the subsurface away from or downgradient of
where the primary oxidant is introduced.
47. The method of claim 1, wherein a reducing environment is
established in a region of the subsurface, and wherein an oxidizing
environment is established in a region downgradient of the reducing
environment and/or surrounding the reducing environment by
introducing the primary oxidant and or introducing hydrogen
peroxide.
48. The method of claim 1, further comprising: introducing a
peroxide into the subsurface; wherein the peroxide promotes
proliferation of aerobic microorganisms and biodegradation of the
biodegradable compound.
49. The method of claim 1, wherein the contaminant comprises a
component selected from the group consisting of NAPL (non-aqueous
phase liquid), DNAPL (dense non-aqueous phase liquid), LNAPL (light
non-aqueous phase liquid), aromatic hydrocarbon, non-halogenated
aromatic hydrocarbon, polyaromatic hydrocarbon, BTEX (benzene,
toluene, ethyl benzene, and/or xylene), halogenated hydrocarbon,
and combinations.
50. (canceled)
51. The method of claim 1, wherein the primary oxidant and the
surfactant and/or cosolvent are simultaneously administered.
52. The method of claim 1, wherein the primary oxidant and the
surfactant and/or cosolvent are sequentially administered.
53. The method of claim 1, wherein the primary oxidant oxidizing
the solubilized contaminant and the microorganism biodegrading the
biodegradable compound reduces the amount of contaminant in the
subsurface to less than a predetermined level.
54. The method of claim 1, wherein the amount of residual primary
oxidant remaining after oxidation of the solubilized contaminant is
less than a predetermined level.
55. The method of claim 1, wherein the amount of residual
surfactant and/or cosolvent remaining after oxidation of the
solubilized contaminant is less than a predetermined level.
56. A method of designing a procedure for reducing the
concentration of a contaminant at a site in a subsurface,
comprising: obtaining a sample representative of the contaminated
site of interest; testing the sample with various concentrations of
primary oxidant, surfactant, and/or cosolvent under various
conditions of temperature, pressure, and/or flow rate; determining
the rate of mobilization of the contaminant under the various
concentrations and conditions; determining the rate of
biodegradation of the contaminant under the various concentrations
and conditions; and identifying an optimum set of concentrations
and conditions for reducing the concentration of the contaminant at
the site in the subsurface, wherein the representative sample is
selected from the group consisting of a core sample taken from the
subsurface of the site and a simulated sample comprising soil
similar to that of the subsurface of the site spiked with
contaminant.
57. (canceled)
58. A system for reducing the concentration of a contaminant at a
site in a subsurface, comprising: an injection well; an injection
fluid injection system fluidly connected to the injection well; an
injection fluid comprising a primary oxidant and a surfactant
and/or a cosolvent, the system being operable to promote
biodegradation of the contaminant.
59. The system of claim 58, comprising: a first pumping system that
stores a primary oxidant and a surfactant and/or a cosolvent, mixes
the primary oxidant and the surfactant and/or cosolvent in
predetermined ratios, and injects the primary oxidant and the
surfactant and/or cosolvent at a first injection point into an
oxidation zone of the subsurface at a predetermined rate; a second
pumping system that stores a reducing agent and injects the
reducing agent at a second injection point into a reducing zone of
the subsurface at a predetermined rate; a monitoring device that
determines the concentration and/or spatial distribution in the
subsurface of a quantity selected from the group consisting of
contaminant, oxidant, surfactant, cosolvent, microorganisms, and
combinations; wherein the monitoring device can adjust the ratios
of mixing the primary oxidant and the surfactant and/or cosolvent,
the rate of injection of the primary oxidant and the surfactant
and/or cosolvent, and the rate of injection of the reducing agent
so as to maximize biodegradation by the microorganisms, minimize
the concentration of the contaminant, minimize the time required to
reduce the contaminant to a predetermined level, and/or minimize
the amount of primary oxidant, surfactant, cosolvent, and/or
reducing agent used.
Description
BACKGROUND
[0001] The present invention relates to methods and compositions
for remediating soil and groundwater. For example, the present
invention relates to methods and compositions for removing
contaminants from soil and groundwater in situ using surfactants or
surfactant-cosolvent mixtures and oxidants to induce chemical
oxidation and biodegradation.
[0002] Bioremediation can use organisms such as green plants,
bacteria, fungi, or microorganisms to return an environment altered
by contaminants to its original condition. Examples of
bioremediation include attacking specific soil contaminants, such
as chlorinated hydrocarbons, by bacteria, and cleaning up oil
spills by the addition of fertilizers (such as nitrate and sulfate
fertilisers) that facilitate the bacterial decomposition of crude
oil. For a long time, phytoextraction has been used to desalinate
agricultural land. Examples of bioremediation technologies include
bioventing, landfarming, bioreactor, composting, bioaugmentation,
rhizofiltration, and biostimulation.
SUMMARY
[0003] A method according to the invention for reducing the
concentration of a contaminant in a subsurface to a predetermined
level can include the following. A primary oxidant and a surfactant
and/or a cosolvent can be introduced into the subsurface. The
surfactant can solubilize and/or desorb the contaminant. The
primary oxidant can oxidize the solubilized contaminant in the
subsurface to a biodegradable compound. A microorganism in the
subsurface can biodegrade the biodegradable compound. The method
can reduce the concentration of the contaminant in the subsurface
to the predetermined level.
[0004] The method can include monitoring the subsurface for a
quantity selected from the group consisting of contaminant
concentration, oxidant concentration, surfactant concentration,
cosolvent concentration, microorganism concentration, and
combinations. The information obtained by monitoring can be used to
adjust the amount of oxidant, surfactant, and/or cosolvent
introduced into the subsurface to minimize the amount of
contaminant in the subsurface.
[0005] The method can include establishing an oxidative zone in the
subsurface with the primary oxidant in the vicinity of the locus of
introduction of the primary oxidant. Aerobic microorganisms can
proliferate in the oxidative zone and biodegrade the biodegradable
compound and/or the contaminant. Oxidation of the solubilized
contaminant and/or biodegradation of the biodegradable compound by
the microorganism can consume the primary oxidant and can establish
a reductive zone in the subsurface surrounding the oxidative zone.
Anaerobic microorganisms can proliferate in the reductive zone and
biodegrade the biodegradable compound and/or the contaminant.
[0006] A method according to the invention of designing a procedure
for reducing the concentration of a contaminant at a site in a
subsurface can include the following. A sample representative of
the contaminated site of interest can be obtained. The sample can
be tested with various concentrations of primary oxidant,
surfactant, and/or cosolvent under various conditions of
temperature, pressure, and/or flow rate. The rate of mobilization
of the contaminant under the various concentrations and conditions
can be determined. The rate of biodegradation of the contaminant
under the various concentrations and conditions can be determined.
An optimum set of concentrations and conditions for reducing the
concentration of the contaminant at the site in the subsurface can
be identified.
[0007] In an embodiment according to the invention, a system for
reducing the concentration of a contaminant at a site in a
subsurface can include an injection well, an injection fluid
injection system fluidly connected to the injection well, and an
injection fluid. The injection fluid can include a primary oxidant
and a surfactant and/or a cosolvent. The system can operate to
promote biodegradation of the contaminant.
[0008] The system can include a first pumping system and a second
pumping system. The first pumping system can store a primary
oxidant and a surfactant and/or a cosolvent, mix the primary
oxidant and the surfactant and/or cosolvent in predetermined
ratios, and inject the primary oxidant and the surfactant and/or
cosolvent at a first injection point into an oxidation zone of the
subsurface at a predetermined rate. The second pumping system can
store a reducing agent and inject the reducing agent at a second
injection point into a reducing zone of the subsurface at a
predetermined rate. A monitoring device can determine the
concentration and/or spatial distribution in the subsurface of a
quantity selected from the group consisting of contaminant,
oxidant, surfactant, cosolvent, microorganisms, and combinations.
The monitoring device can adjust the ratios of mixing the primary
oxidant and the surfactant and/or cosolvent, the rate of injection
of the primary oxidant and the surfactant and/or cosolvent, and the
rate of injection of the reducing agent, so as to maximize
biodegradation by the microorganisms, minimize the concentration of
the contaminant, minimize the time required to reduce the
contaminant to a predetermined level, and/or minimize the amount of
primary oxidant, surfactant, cosolvent, and/or reducing agent
used.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1A illustrates processes in a combined
S-ISCO.TM.--reductive biodegradation approach for remediating a
NAPL contaminated site.
[0010] FIG. 1B illustrates the process of oxidation of contaminant
by S-ISCO.
[0011] FIG. 1C illustrates the process of biodegradation of
contaminant.
DETAILED DESCRIPTION
[0012] Embodiments of the invention are discussed in detail below.
In describing embodiments, specific terminology is employed for the
sake of clarity. However, the invention is not intended to be
limited to the specific terminology so selected. A person skilled
in the relevant art will recognize that other equivalent parts can
be employed and other methods developed without parting from the
spirit and scope of the invention. All references cited herein are
incorporated by reference as if each had been individually
incorporated.
S-ISCO.TM.
[0013] Surfactant enhanced in-situ chemical oxidation (S-ISCO.TM.)
remediation can be used to remediate sites, for example,
subsurfaces, in which soil in a subsurface is contaminated by
chemicals of concern (COCs), such as non-aqueous phase liquids
(NAPLs). Surfactant or surfactant-cosolvent mixtures can be
injected to create an effective solubilized micelle or
microemulsion, for example, a Windsor I system, with the COC
present in the soil. This solubilized micelle or microemulsion can
increase the apparent solubility of the COC, so that the
solubilized micelle or microemulsed COC is able to enter into
"aqueous phase reactions." In the case of S-ISCO.TM. remediation,
the COC can be oxidized using a primary oxidant such as
permanganate, ozone, persulfate, activated persulfate,
percarbonate, activated percarbonate, or hydrogen peroxide, or
ultraviolet (uV) light or any combination of these oxidants with or
without uV light. Several methods can be used to activate or
catalyze peroxide and persulfate to form free radicals such as free
or chelated transition metals and uV light. Persulfate can be
additionally activated at both high and low pH, by heat or by
peroxides, including calcium peroxides. Persulfate and ozone can be
used in a dual oxidant mode with hydrogen peroxide.
[0014] Although remediation systems that rely on Winsor Type I
solubilized micelle or microemulsification can be less efficient
than those that rely on Winsor Type III microemulsions and
mobilization, the desorption and solubilization of contaminants
using Winsor Type I microemulsions are controllable such that the
risk of off-site mobilization of NAPL chemicals of concern (COCs)
is minimal and that complete recovery of injected chemicals,
mobilized COC phases, and solubilized COC or sorbed chemicals using
extraction wells is not required. Under solubilizing conditions,
the NAPL removal rate can be dependent on the increase in
solubility of the NAPL in the surfactant mixture. Under desorbing
conditions, the sorbed COC species removal rate can be dependent on
the rate of desorption of the COC into the surfactant or
surfactant-cosolvent mixture.
[0015] The S-ISCO.TM. process includes a method and process of
increasing the solubility of contaminants, such as normally low
solubility nonaqueous phase liquids (NAPLs), sorbed contaminants,
or other chemicals in soils in surface and ground water.
Simultaneously or subsequently, the contaminating chemicals are
oxidized using a chemical oxidant without the need of extraction
wells for the purpose of recovering the injected cosolvents and/or
surfactants with NAPL compounds. Examples of contaminants are dense
nonaqueous phase liquids (DNAPLs), light nonaqueous phase liquids
(LNAPLs), nonaqueous phase liquids (NAPLs), sorbed contaminants,
polycyclic aromatic hydrocarbons (PAHs), chlorinated solvents,
pesticides, herbicides, polychlorinated biphenyls, and various
organic chemicals, such as petroleum hydrocarbons and their
products. Contaminants can be associated with, for example,
manufactured gas plant residuals, creosote wood treating liquids,
petroleum residuals, pesticide, or polychlorinated biphenyl (PCB)
residuals and other waste products or byproducts of industrial
processes and commercial activities. Contaminants may be in the
liquid phase, for example, NAPLs, sorbed to the soil matrix, or in
the solid phase, for example, certain pesticides.
[0016] A subsurface can include any and all materials below the
surface of the ground, for example, groundwater, soils, rock,
man-made structures, naturally occurring or man-made contaminants,
waste materials, or products. Knowledge of the distribution of
hydraulic conductivity in the soil and other physical
hydrogeological subsurface properties, such as hydraulic gradient,
saturated thickness, soil heterogeneity, and soil type is desirable
to determine, for example, the relative contribution of downward
vertical density driven flow to normal advection in the
subsurface.
[0017] The composition of a surfactant and/or cosolvent liquid
amendment for injection into a subsurface can include a natural
surfactant or a surfactant derived from a natural product, such as
a plant oil or plant extract. Mixtures of these natural surfactants
or surfactants derived from natural products can be chosen to best
emulsify the subsurface contaminant, e.g., NAPL, LNAPL, or DNAPL,
such that a mobile phase emulsion is formed with greatly differing
properties from the source contaminant. The choice of surfactants
and/or cosolvents can be based on the testing of the source
contaminant. For example, a surfactant and/or cosolvent mixture can
be selected to produce a low interfacial tension that enables the
formation of either Winsor Type I, Winsor Type II, or Winsor Type
III systems. A preferred formation of microemulsions is to form
Winsor Type III microemulsions or Winsor Type I microemulsions.
Frequently the preferred natural solvent such as those derived from
plants are generally biodegradable, including terpenes. Terpenes
are natural products extracted from conifer and citrus plants, as
well as many other essential oil producing species. The combination
of cosolvent and surfactants enhances the formation of
microemulsions from a contaminant, e.g., a NAPL, LNAPL, or DNAPL.
The specific choice of natural cosolvents and the ratio of
cosolvent to surfactant can be based on laboratory tests conducted
on the contaminant to be emulsified. All of the above natural
surfactants, surfactants derived from natural oils and natural
cosolvents can be combined into formulations to form non- or
low-toxicity macroemulsions and microemulsions, with contaminants,
enhancing their recovery, and, thus, elimination from a
contaminated subsurface. Once emulsified, the
contaminant-surfactant-cosolvent system is formed, so that the
contaminant is amenable to become mobile in the subsurface.
[0018] For example, a method for reducing the concentration of a
contaminant at a site in a subsurface can include the following.
The contaminant can, for example, include a non-aqueous phase
liquid (NAPL), a dense non-aqueous phase liquid (DNAPL), and/or a
light non-aqueous phase liquid (LNAPL). An extraction well can be
provided in the subsurface; for example, the extraction well can
remove bulk quantities of contaminant. An injection fluid can be
injected at an injection locus into the subsurface. The injection
fluid can include hydrogen peroxide and/or another oxidant, or
another gas phase generating oxidant or pressure dissolved gas in a
liquid. The hydrogen peroxide and/or the other oxidant or dissolved
gas can be allowed to decompose to liberate oxygen or dissolved gas
in the subsurface. The other oxidant can be, for example, ozone, a
persulfate, sodium persulfate, or a percarbonate. The injection
fluid can include a liquid, e.g., water, and a dissolved gas, e.g.,
oxygen and/or carbon dioxide, and the dissolved gas can effervesce
as a liberated gas upon a decrease of pressure on the injection
fluid in the subsurface. The injection fluid can include a
compressed gas and/or a supercritical fluid under a pressure
greater than atmospheric. An injected gas can include, for example,
oxygen, carbon dioxide, nitrogen, air, an inert gas, helium, argon,
another gas, or combinations of these. The injection fluid can
include a surfactant and/or a cosolvent, for example, the injection
fluid can include VeruSOL. The injection fluid can include an
alkali carbonate or bicarbonate, such as sodium bicarbonate. The
injection fluid can include an activator, for example, a metal
activator, a chelated metal activator, a chelated iron activator,
Fe-NTA, Fe(II)-EDTA, Fe(III)-EDTA, Fe(II)-citric acid, or
Fe(III)-citric acid. The injection fluid can include an
antioxidant. The oxygen and/or the gas produced from reaction of
the oxygen, hydrogen peroxide, and/or other oxidant with the
contaminant, e.g., carbon dioxide, can be allowed to impose
pressure to force the contaminant to flow through the subsurface
toward the extraction well. The contaminant can be removed from the
extraction well to a surface above the subsurface. The contaminant
can then be stored, for example, in a storage tank, or can be
disposed of, for example, in a waste destruction facility. A wide
range of configurations can be used to implement facilitated
remediation by extraction aided by gas pressure in conjunction with
ISCO or S-ISCO. The selection of a configuration for remediation of
a site can be guided by considerations of, for example, the nature
of the contaminant, hydrogeology of the site, economics of
procedures such as well drilling and waste disposal, and costs of
chemicals such as oxidants, cosolvents, and surfactants.
[0019] In implementing S-ISCO, the surfactant or
surfactant-cosolvent mixture can be introduced sequentially or
simultaneously (together) with the oxidant into a subsurface. For
example, the surfactant or surfactant-cosolvent mixture can first
be introduced, then the oxidant and/or other injectants can be
introduced. Alternatively, the oxidant can first be introduced,
then the surfactant or surfactant-cosolvent mixture can be
introduced. Alternatively, the oxidant and the surfactant or
surfactant-cosolvent mixture can be introduced simultaneously.
Simultaneously can mean that the oxidant and the surfactant and/or
cosolvent are introduced within 6 months of each other, within 2
months of each other, within 1 month of each other, within 1 week
of each other, within 1 day of each other, within one hour of each
other, or together, for example, as a mixture of oxidant with
surfactant and/or cosolvent. In each case, the oxidant is present
in sufficient amounts at the right time, together with the
surfactant, to oxidize contaminants as they are solubilized or
mobilized by surfactant or cosolvent-surfactant mixture.
[0020] For example, shallow contamination near the water table can
be effectively targeted by using persulfate concentrations in the,
say, 10 g/L (grams per liter) to 15 g/L range and moderately high
injection flowrates, e.g., up to 30 gpm (gallons per minute) per
injection location, dependent on the geometry of the injection
trench or wells. For intermediate depth locations, persulfate
concentrations up to, say, 25 g/L can be used with, e.g., up to 20
gpm per injection, dependent on the geometry of the injection
trench or wells. For deeper DNAPL contamination, persulfate
concentrations up to 100 g/L can be used dependent on the nature of
the DNAPL distributions and concentrations. Injection flowrates for
deep DNAPL applications can be up to, say, 20 gpm per well, if
injected above the lower permeability layers and up to, say, 10 gpm
per well, if injected in the lower permeability unit. For certain
subsurfaces, it may be advantageous to inject substances such as
oxidants, surfactants, and/or cosolvents under elevated pressure.
Unlike permanganate, persulfate forms no significant solid phase
precipitates.
[0021] A goal in the remediation of sites containing large
quantities of contaminants, such as LNAPLs and DNAPLs, is to obtain
the benefits of ISCO (in-situ chemical oxidation) or S-ISCO
(surfactant enhanced in-situ chemical oxidation) in destroying the
contaminants without mobilizing them off site, while reducing the
quantity and thus the cost of the oxidant injected.
[0022] In an embodiment, a user creates a localized zone in the
subsurface for the extraction of large quantities of contaminants,
such as LNAPLs or DNAPLs (extraction zone), while having chemical
oxidation of the contaminants take place in the subsurface beyond
the extraction zone. The contaminants extracted may either be in a
phase-separated state or in a solubilized or emulsified state. By
creating a zone of chemical oxidation of the contaminants beyond
the localized extraction zone, the risks associated with incomplete
extraction of contaminants, such as LNAPLs or DNAPLs, inherent in
traditional SEAR (surfactant-enhanced aquifer remediation)
applications are minimized or eliminated. That is, in a process
according the invention, a zone of chemical oxidation (oxidation
zone), a zone of biodegradation by aerobic microorganisms, and/or a
zone of biodegradation by anaerobic microorganisms surrounding the
extraction zone serves to destroy any contaminant that migrates out
of the extraction zone, and thus prevents the spread of
contaminant. Thus, the simultaneous use of the S-ISCO (surfactant
enhanced in-situ chemical oxidation) process with extraction of the
solubilized or emulsified LNAPLs and/or DNAPLs minimizes the risk
from migration of NAPLs.
[0023] At the same time, by employing liquid extraction using
single and/or dual phase pumping systems, for example, of the types
that are commonly known in the art, the amount of oxidant chemical
required may be less than that when ISCO (in-situ chemical
oxidation) or S-ISCO (surfactant enhanced in-situ chemical
oxidation) is used alone. At sites with large quantities of LNAPLs
and/or DNAPLs, the cost of liquid extraction of contaminants, such
as LNAPLs and/or DNAPLs, coupled with ISCO or S-ISCO may be less
than using ISCO or S-ISCO alone. That is, the cost of extraction
and subsequent on site treatment or off-site disposal of the
contaminants may be offset by the savings represented by the
decrease in the quantity of oxidant and/or other chemicals
required. Thus, sites containing large quantities of contaminants,
such as LNAPLs or DNAPLs, can be cost-effectively treated.
[0024] Additional description of the S-ISCO.TM. process can be
found in the international application PCT/US2007/007517, published
as WO2007/126779, which is hereby incorporated by reference.
Surfactants and Cosolvents
[0025] Surfactant or surfactant-cosolvent mixtures to solubilize
NAPL components and desorb contaminants of concern (COCs) from site
soils or from NAPL in water mixtures can be screened for use in a
combined surfactant-oxidant treatment. For example, blends of
biodegradable citrus-based solvents (for example, d-limonene) and
degradable surfactants derived from natural oils and products can
be used.
[0026] For example, a composition of surfactant and cosolvent can
include at least one citrus terpene and at least one surfactant. A
citrus terpene may be, for example, CAS No. 94266-47-4, citrus
peels extract (citrus spp.), citrus extract, Curacao peel extract
(Citrus aurantium L.), EINECS No. 304-454-3, FEMA No. 2318, or FEMA
No. 2344. A surfactant may be a nonionic surfactant. For example, a
surfactant may be an ethoxylated castor oil, an ethoxylated coconut
fatty acid, or an amidified, ethoxylated coconut fatty acid. An
ethoxylated castor oil can include, for example, a polyoxyethylene
(20) castor oil, CAS No. 61791-12-6, PEG (polyethylene glycol)-10
castor oil, PEG-20 castor oil, PEG-3 castor oil, PEG-40 castor oil,
PEG-50 castor oil, PEG-60 castor oil, POE (polyoxyethylene) (10)
castor oil, POE(20) castor oil; POE (20) castor oil (ether, ester);
POE(3) castor oil, POE(40) castor oil, POE(50) castor oil, POE(60)
castor oil, or polyoxyethylene (20) castor oil (ether, ester). An
ethoxylated coconut fatty acid can include, for example, CAS No.
39287-84-8, CAS No. 61791-29-5, CAS No. 68921-12-0, CAS No.
8051-46-5, CAS No. 8051-92-1, ethoxylated coconut fatty acid,
polyethylene glycol ester of coconut fatty acid, ethoxylated
coconut oil acid, polyethylene glycol monoester of coconut oil
fatty acid, ethoxylated coco fatty acid, PEG-15 cocoate, PEG-5
cocoate, PEG-8 cocoate, polyethylene glycol (15) monococoate,
polyethylene glycol (5) monococoate, polyethylene glycol 400
monococoate, polyethylene glycol monococonut ester, monococonate
polyethylene glycol, monococonut oil fatty acid ester of
polyethylene glycol, polyoxyethylene (15) monococoate,
polyoxyethylene (5) monococoate, or polyoxyethylene (8)
monococoate. An amidified, ethoxylated coconut fatty acid can
include, for example, CAS No. 61791-08-0, ethoxylated reaction
products of coco fatty acids with ethanolamine, PEG-11 cocamide,
PEG-20 cocamide, PEG-3 cocamide, PEG-5 cocamide, PEG-6 cocamide,
PEG-7 cocamide, polyethylene glycol (11) coconut amide,
polyethylene glycol (3) coconut amide, polyethylene glycol (5)
coconut amide, polyethylene glycol (7) coconut amide, polyethylene
glycol 1000 coconut amide, polyethylene glycol 300 coconut amide,
polyoxyethylene (11) coconut amide, polyoxyethylene (20) coconut
amide, polyoxyethylene (3) coconut amide, polyoxyethylene (5)
coconut amide, polyoxyethylene (6) coconut amide, or
polyoxyethylene (7) coconut amide.
[0027] Examples of surfactants and/or cosolvents that can be used
include terpenes, citrus-derived terpenes, limonene, d-limonene,
castor oil, coca oil, coconut oil, soy oil, tallow oil, cotton seed
oil, and a naturally occurring plant oil. The surfactant and/or
cosolvent can be a nonionic surfactant, such as ethoxylated soybean
oil, ethoxylated castor oil, ethoxylated coconut fatty acid, and
amidified, ethoxylated coconut fatty acid. The surfactant and/or
cosolvent can be ALFOTERRA 123-8S, ALFOTERRA 145-8S, ALFOTERRA
L167-7S, ETHOX HCO-5, ETHOX HCO-25, ETHOX CO-5, ETHOX CO-40, ETHOX
ML-5, ETHAL LA-4, AG-6202, AG-6206, ETHOX CO-36, ETHOX CO-81, ETHOX
CO-25, ETHOX TO-16, ETHSORBOX L-20, ETHOX MO-14, S-MAZ 80K, T-MAZ
60 K 60, TERGITOL L-64, DOWFAX 8390, ALFOTERRA L167-4S, ALFOTERRA
L123-4S, and ALFOTERRA L145-4S.
[0028] Examples of surfactants derived from natural plant oils are
ethoxylated coca oils, coconut oils, soybean oils, castor oils,
corn oils and palm oils. Many of these natural plant oils are US
FDA GRAS.
[0029] Compositions for use as surfactant and/or cosolvent liquid
amendments for subsurface injection can include natural
biodegradable surfactants and cosolvents. Natural biodegradable
surfactants can include those that occur naturally, such as yucca
extract, soapwood extract, and other natural plants that produce
saponins, such as horse chestnuts (Aesculus), climbing ivy
(Hedera), peas (Pisum), cowslip, (Primula), soapbark (Quillaja),
soapwort (Saponaria), sugar beet (Beta) and balanites (Balanites
aegyptiaca). Many surfactants derived from natural plant oils are
known to exhibit excellent surfactant power, and are biodegradable
and do not degrade into more toxic intermediary compounds.
[0030] Examples of cosolvents which preferentially partition into
the NAPL phase include higher molecular weight miscible alcohols
such as isopropyl and tert-butyl alcohol. Alcohols with a limited
aqueous solubility such as butanol, pentanol, hexanol, and heptanol
can be blended with the water miscible alcohols to improve the
overall phase behavior. Given a sufficiently high initial cosolvent
concentration in the aqueous phase (the flooding fluid), large
amounts of cosolvent partition into the NAPL. As a result of this
partitioning, the NAPL phase expands, and formerly discontinuous
NAPL ganglia can become continuous, and hence mobile. This
expanding NAPL phase behavior, along with large interfacial tension
reductions, allows the NAPL phase to concentrate at the leading
edge of the cosolvent slug, thereby increasing the mobility of the
NAPL. Under certain conditions, a highly efficient piston-like
displacement of the NAPL is possible. Because the cosolvent also
has the effect of increasing the NAPL solubility in the aqueous
phase, small fractions of the NAPL which are not mobilized by the
above mechanism are dissolved by the cosolvent slug.
[0031] The surfactants/cosolvents Citrus Burst 1, Citrus Burst 2,
Citrus Burst 3, and E-Z Mulse are manufactured by Florida
Chemical.
Combined S-ISCO.TM. and Biodegradation
[0032] The S-ISCO process can be performed in combination with a
biodegradation (bioremediation) process. Combining S-ISCO and
biodegradation processes can result in several advantageous
synergies. For example, a surfactant, such as VeruSOL can gives
give an oxidant access to contaminants, so that the oxidant
oxidizes the contaminant. A surfactant, such as VeruSOL, can then
provide a source of carbon as well as nitrogen and phosphorous
nutrients to stimulate proliferation of native microorganisms. For
example, persulfate can provide a source of electron acceptor to
"sulfideogenic bacteria" that then can further break down
contaminants. Other sources of carbon for microorganisms include
organic compounds partially degraded by injected (e.g. persulfate)
oxidant; the compounds may be more accessible to the microorganisms
in a partially degraded state. Other sources of carbon for
microorganisms include undegraded organic contaminant compounds and
naturally present subsurface organic compounds.
[0033] The S-ISCO part of a combined process can allow for faster
elimination of contaminants than bioremediation alone. The
bioremediation part of a combined process can supplement S-ISCO by
further degrading contaminant partially oxidized by S-ISCO, and can
complement S-ISCO, for example by degrading contaminants that may
be resistant to chemical oxidation. The bioremediation part of a
combined process can also reduces the amount required of injected
remediation chemicals, e.g., oxidant and surfactant, which can
reduce the cost of remediation. Furthermore, the bioremediation
part of a combined process can eliminate residual surfactant and
residual oxidant remaining after destruction of the contaminant.
This can prevent the residual surfactant and residual oxidant from
becoming contaminants themselves, and can allow for the use of
excess surfactant and oxidant at the beginning of a remediation
process so as to achieve faster remediation.
[0034] Some observations in a S-ISCO pilot test in the field of a
remediation process indicate that contaminant levels and persulfate
levels continue to decrease after the injection of persulfate
oxidant ceases, and may indicate that native microorganisms
biodegrade contaminant and may have been stimulated by the injected
substances.
[0035] Surfactant enhanced in-situ chemical oxidation (S-ISCO.TM.)
remediation of hydrocarbon contaminants can yield products other
than those associated with complete oxidation. For example,
S-ISCO.TM. treatment of a high-molecular weight hydrocarbon can
yield partially oxidized hydrocarbons of intermediate molecular
weight, rather than only carbon dioxide and water.
[0036] In an embodiment, partially oxidized hydrocarbons can be
allowed to remain in the soil, where they are further degraded to
lower molecular weight species by microorganisms in the soil. For
example, an oxidant such as sodium persulfate can be injected into
the soil where a contaminant is present to induce primary or
chemical oxidation. The oxidant may completely or only partially
oxidize the contaminant. The partially oxidized contaminant can,
for example, diffuse to a different region, be displaced by a
convective flow, for example, the flow of groundwater, or remain
where it is. For example, the subsurface can have a downgradient
direction and can include groundwater. The groundwater can flow in
the downgradient direction, and transport the partially oxidized
contaminant with it. For example, downgradient of the point or
locus where the oxidant is introduced can refer to at least about
150 ft, 200 ft, 250 ft, or 275 feet downgradient of the oxidant
injection locus. Alternatively, the injection of material at a
point, for example, surfactant, oxidant, and water at the source of
contamination, can flow outward from the point, and transport
partially oxidized contaminant with it.
[0037] Microorganisms present in the soil, such as aerobic or
anaerobic microbes, can further oxidize the contaminant or
reductively break down the contaminant.
[0038] Combining biodegradation with the injection of a primary
oxidant, such as sodium persulfate, can provide a number of
benefits. The primary oxidant can induce the rapid chemical
oxidation of the contaminant. Even if the contaminant is not fully
oxidized, the partially oxidized products can be less harmful than
the initial contaminant.
[0039] By contrast, a biodegradation approach alone may proceed
rather slowly. Biodegradation reactions can take place in the
dissolved phase, and the low solubility of organic contaminants in
the dissolved phase and the slow rate of their transfer to the
dissolved phase can limit the overall rate of biodegradation.
Furthermore, the rate at which microorganisms metabolize
contaminants can be slow, so that even if a surfactant is used to
increase the rate of mass transfer to the dissolved phase, the rate
of biodegradation can still be slow. Because of the slow rate of
biodegradation, the dissolved contaminants can be mobilized away
from the initial site of contamination. In so spreading, the
dissolved contaminants can cause harm before they are biodegraded.
Thus, a biodegradation approach alone may not be optimal for
treating the source zone of a contaminated site, which has a high
concentration of contaminants that cannot be sufficiently rapidly
destroyed by biodegradation alone. The slow progress of anaerobic
degradation can render remediation unacceptable from a practical or
business standpoint.
[0040] Furthermore, for an exclusively reductive biodegradation
process, a large amount of material required to serve as food for
aerobic microorganisms may need to be provided. For anaerobic
microorganisms, a material that can react with oxygen (which can be
food for aerobic microorganisms that causes the aerobic
microorganisms to consume oxygen) may need to be added in order to
consume available oxygen and establish a reductive environment.
[0041] However, biodegradation can be a valuable adjuvant to the
S-ISCO.TM. process. For example, an oxidative environment may be
present away from the site of primary injection where the majority
of chemical oxidation proceeds. Even if strict chemical oxidation
does not take place at a sufficient rate in this removed oxidative
environment, certain aerobic microorganisms in the soil can make
use of the available oxygen to degrade remaining unoxidized
contaminant or partially oxidized contaminant. The use of such
aerobic microorganisms may result in a more complete destruction of
the contaminant, may allow for the amount of primary oxidant
injected to be reduced, thus reducing cost, or may allow for
treatment by biodegradation of contaminant to continue far from the
site of injection of the primary oxidant, for example, when
groundwater carries contaminant downgradient in a plume.
[0042] Certain contaminants, for example, halogenated hydrocarbons,
may exhibit some resistance to degradation by chemical oxidation.
In such a case, chemical oxidation induced by injection of a
primary oxidant, such as sodium persulfate, can be complemented by
reduction of the remaining contaminants or products by anaerobic
microorganisms in a region with a reducing environment removed from
the region where chemical oxidation occurs.
[0043] In a combined S-ISCO.TM.--biodegradation approach, chemical
addition can be limited to the contaminant source zone. The organic
carbon dissolved by VeruSOL and degraded COCs and nutrients from
VeruSOL can then migrate downgradient in the plume. S-ISCO.TM. can
solubilize NAPLs rapidly and simultaneously and rapidly oxidize the
solubilized compounds. Any unoxidized or partially oxidized
compounds remaining from S-ISCO.TM. can consume available oxygen to
create reducing zones in which anaerobic processes like reductive
dechlorination can take place.
[0044] For example, the destruction of contaminants in soil in the
subsurface can proceed as follows. The primary oxidant injected can
partially or fully oxidize contaminants susceptible to oxidation,
such as aromatic hydrocarbons. Contaminants resistant to oxidation,
such as certain halogenated organics, may be only partially
oxidized or not oxidized at all. At some distance from the primary
oxidant injection site, the concentration of oxygen can decrease,
so that although an oxidizing environment is still present, the
rate of chemical oxidation is low. In this region, aerobic
microorganisms can continue to degrade contaminant. Still farther
from the primary oxidant injection site, the oxidation potential
can decrease, for example, can decrease to less than zero, so that
a reducing environment is present. In the reducing environment,
anaerobic microorganisms can degrade contaminants, for example,
contaminants that are resistant to oxidation, such as halogenated
organics.
[0045] S-ISCO.TM. generates products of partial oxidation that are
easy to biodegrade compounds (and can serve as a food source for
microorganisms) from both contaminants and from naturally
biodegradable cosolvents and surfactants used for S-ISCO.TM.. As
the natural cosolvents and surfactants used undergo oxidation, they
become more easily naturally biodegraded. The production of easy to
biodegrade compounds from both the organic liquids and the
cosolvent/surfactants may require more electron acceptors (i.e.,
oxygen in the case of aerobic biodegradation and in the case of
anaerobic biodegradation alternative electron acceptors).
[0046] Nutrients, for example, an inorganic or an organic
substance, for example, a micronutrient or a macronutrient, can be
injected into the subsurface to stimulate the growth of
microorganisms, for example, aerobic or anaerobic microorganisms.
Such a nutrient can be a mineral, for example, potassium persulfate
or ammonium persulfate. Thus, the primary oxidant can also serve as
a nutrient. For example, the surfactants injected as part of the
S-ISCO process can serve as a source of food and/or nutrients for
microorganisms. For example, the plant-derived surfactants present
in VeruSOL can include carbon, nitrogen and phosphorous, which can
be useful as food and nutrients to microorganisms. For example,
oxidants injected can serve as a source of food and/or nutrients
for microorganisms. For example, the oxidants potassium persulfate
and/or ammonium persulfate can serve as nutrient sources of
potassium and nitrogen. Thus, in designing a remediation process,
the selection of compounds used for S-ISCO, such as surfactants and
oxidants, can be influenced by the synergistic role they can play
in promoting the growth and metabolism of microorganisms that
biodegrade contaminants and/or partially oxidized products of
contaminants.
[0047] Furthermore, in designing a remediation process, certain
compounds can be introduced to the site to be remediated, for
example, a subsurface, primarily for their role in promoting the
growth and metabolism of microorganisms. The nutrient can include
an organic or inorganic (e.g., mineral) compound or other substance
that promotes the growth of microorganisms. For example,
macronutrients and/or micronutrients can be injected. For example,
at some distance from a locus where a primary oxidant is injected
for S-ISCO, a reductant can be injected to induce a reductive
environment to promote the growth and metabolism of anaerobic
microorganisms. Alternatively, at some distance from a locus where
a primary oxidant is injected for S-ISCO, an oxidant can be
injected to induce an oxidative environment to promote the growth
and metabolism of aerobic microorganisms.
[0048] S-ISCO.TM. can be used to create source zone treatment. At
the same time, S-ISCO.TM. can generate easily biodegradable organic
chemicals from contaminants and solubilize organic NAPLs, to
promote the biodegradation treatment of soil and groundwater plumes
located downgradient of a source zone.
[0049] The coupling of S-ISCO.TM. with bioremediation for
remediation overcomes several major limitations of bioremediation
alone. The S-ISCO.TM. and bioremediation coupled approach overcomes
NAPL solubility and desorption limitations that restrict mass
transfer to the aqueous phase. S-ISCO.TM. can rapidly break down
environmental contaminants, and lessen the amount of total
contaminant that the slower biodegradation processes need to break
down. Many environmental contaminants are difficult to biodegrade,
but their oxidation products can be readily biodegraded; thus,
S-ISCO.TM. can produce oxidation products that are then
biodegraded.
[0050] The oxidation rates of compounds associated with source area
organic liquids, NAPLs, and sorbed COCs using S-ISCO.TM. are much
faster than those achievable using biodegradation alone in the
subsurface. Downgradient from source area S-ISCO.TM. treatment, it
may be cost effective to use natural or stimulated biodegradation
for contaminated plume management and treatment.
[0051] Surfactants or mixtures of cosolvents and surfactants
together with chemical oxidants can be used to solubilize and
oxidize organic liquids, NAPLs, and/or sorbed organic chemicals in
contaminant source zones. These organic liquids, NAPLs, and/or
sorbed organic chemicals and/or their oxidation products can then
subsequently be biologically or enzymatically degraded, either
aerobically or anaerobically. Naturally biodegradable surfactants
or cosolvent/surfactants can be used, so that these can be
aerobically or anaerobically biodegraded along with the organic
liquids, NAPLs, and/or sorbed organic chemicals and/or their
oxidation products.
[0052] Some contaminants when partially oxidized can be more
susceptible to degradation by aerobic microorganisms, whereas other
contaminants when partially oxidized can be more susceptible to
degradation by anaerobic microorganisms. For example,
non-halogenated aromatic hydrocarbons and partially oxidized
non-halogenated aromatic hydrocarbons can be degraded by aerobic
microorganisms. On the other hand, halogenated organics and
partially oxidized halogenated organics can be degraded by
anaerobic microorganisms. Thus, an approach to performing in-situ
remediation of a contaminant can be developed based on the type of
the contaminant present in a subsurface.
[0053] In an embodiment, a microorganism can be introduced into the
subsurface, for example, to "seed" the subsurface and thereby
promote biodegradation. For example, an aerobic microorganism
and/or an aerobic microorganism can be introduced into the
subsurface.
[0054] Microorganisms such as Burkholderia, Burkholderia
xenovorans, Rhodococcus, Aromatoleum aromaticum, Geobacter
metallireducens, Dechloromonas aromatica, Dehalococcoides,
Dehalococcoides ethenogenes, Desulfitobacterium hafniense,
Pseudomonas, Pseudomonas alcaligenes, Pseudomonas mendocina,
Pseudomonas resinovorans, Pseudomonas veronii, Pseudomonas putida,
Pseudomonas stutzeri, Deinococcus radiodurans are capable of
biodegrading hydrocarbons, such as aromatic hydrocarbons and
halogenated hydrocarbons.
[0055] For example, S-ISCO and aerobic and/or anaerobic
biodegradation can be used to reduce the amount or concentration of
a contaminant at a site, e.g., in a subsurface, to a predetermined
level. For example, a predetermined level of a contaminant can be a
maximum amount of a contaminant at a site permitted by law or can
be a maximum concentration of a contaminant permitted by law.
Oxidative Zones: Oxidants, Activators, and Antioxidants
[0056] Oxygen sources for chemical oxidation of contaminants and/or
for the stimulation of aerobic biodegradation of contaminants can
come from injection of oxygen from air or pure oxygen, ozone, solid
oxides, and peroxides or other means of introducing oxygen into the
subsurface or above ground. For example, a persulfate, sodium
persulfate, a percarbonate, a permanganate, potassium permanganate,
and hydrogen peroxide can be introduced into the subsurface or
above ground to provide a source of oxygen.
[0057] If a targeted contaminant can be degraded by aerobic
microorganisms, the growth of aerobic microorganisms can be
encouraged by establishing an oxidative zone or environment.
[0058] Aerobic metabolism by aerobic microorganisms can be
represented by the reaction
O.sub.2+4e.sup.-+4H.sup.+.fwdarw.2H.sub.2O. Aerobic metabolism can
take place, for example, when the environment has a redox
potential, Eh, of from about 600 to about 400 mV.
[0059] For example, in an oxidative environment, aerobic microbes
can further oxidize partially oxidized contaminant that is a
product of treatment of contaminant with an oxidant. Such aerobic
degradation of partially oxidized contaminant can be stimulated by,
for example, introducing an oxidant at a different time or location
or of a different type than associated with the oxidant used to
initially oxidize the contaminant. For example, at a treatment site
where contaminant is moved by groundwater flow, a secondary
oxidant, such as hydrogen peroxide can be injected at a second
injection point downgradient of the point where the primary oxidant
used to initially oxidize the compound, e.g., sodium persulfate,
was added. The injection of hydrogen peroxide can induce or
maintain an oxidative environment in the subsurface, and stimulate
the growth and activity of aerobic microorganisms that break down
contaminant. A secondary oxidant can be the same as or different
from a primary oxidant.
[0060] An activator can be, for example, a chemical molecule or
compound, or another external agent or condition, such as heat,
temperature, or pH, that increases the rate of or hastens a
chemical reaction. The activator may or may not be transformed
during the chemical reaction that it hastens. Examples of
activators which are chemical compounds include a metal, a
transition metal, a chelated metal, a complexed metal, a
metallorganic complex, and hydrogen peroxide. Examples of
activators which are other external agents or conditions include
heat, temperature, and high pH. Preferred activators include
Fe(II), Fe(III), Fe(II)-EDTA, Fe(III)-EDTA, Fe(II)-citric acid,
Fe(III)-citric acid, hydrogen peroxide, high pH, and heat. Zero
valent metals, such as zero valent iron, can serve as activators of
oxidants, for example, hydrogen peroxide.
[0061] Non-thermal ISCO using persulfate can be activated by
ferrous ions or by preferentially chelated metals. Chelated iron
has been demonstrated to prolong the activation of persulfate
enabling activation to take place at substantial distances from
injection wells.
[0062] Several practical sources of Fe(II) or Fe(III) can be
considered for activation of persulfate. Iron present in the soil
minerals that can be leached by injection of a free-chelate (a
chelate not complexed with iron, but usually Na.sup.+ and H.sup.+)
can be a source. Injection of soluble iron as part of a chelate
complex, such as Fe(II)-EDTA, Fe(II)-NTA or Fe(II)-Citric Acid
(other Fe-chelates are available) can be a source. Indigenous
dissolved iron resulting from reducing conditions present in the
subsurface (common at many MGP sites) can be a source. For the
Pilot Test, discussed as an example below, Fe(II)-EDTA was
used.
[0063] An example of an oxidant is persulfate, e.g., sodium
persulfate, of an activator is Fe(II)-EDTA, of a surfactant is
Alfoterra 53, and of a cosolvent-surfactant mixture is a mixture of
d-limonene and biodegradable surfactants, for example, Citrus Burst
3. Citrus Burst 3 includes a surfactant blend of ethoxylated
monoethanolamides of fatty acids of coconut oil and polyoxyethylene
castor oil and d-limonene.
[0064] An embodiment of the invention is the simultaneous or
sequential use of the oxidant persulfate, and an activator to raise
the pH of the groundwater to above 10.5 by the addition of CaO,
Ca(OH).sub.2, NaOH, or KOH, an example of a cosolvent-surfactant is
Citrus Burst 3.
[0065] An aspect of the control that can be achieved by use of an
embodiment of the invention for site remediation is direction of
antioxidant to a target region of contaminant. The density of the
injected solution can be modified, so that the oxidant reaches and
remains at the level in the subsurface of the target region of
contaminant. Additional factors such as subsurface porosity and
groundwater flow can be considered to locate wells for injecting
solution containing oxidant, so that oxidant flows to the target
region of contaminant.
[0066] In an embodiment, the consumption of oxidant can be
controlled by including an antioxidant in the injected solution.
For example, an antioxidant can be used to delay the reaction of an
oxidant. Such control may prove important when, for example, the
injected oxidant must flow through a region of organic matter which
is not a contaminant and with which the oxidant should not react.
Avoiding oxidizing this non-contaminant organic matter may be
important to maximize the efficiency of use of the oxidant to
eliminate the contaminant. That is, if the oxidant does not react
with non-contaminant organic matter, then more oxidant remains for
reaction with the contaminant. Furthermore, avoiding oxidizing
non-contaminant organic matter may be important in its own right.
For example, topsoil or compost may be desirable organic matter in
or on soil that should be retained. The anti-oxidants used may be
natural compounds or derivatives of natural compounds. By using
such natural antioxidants, their isomers, and/or their derivatives,
the impact on the environment by introduction of antioxidant
chemicals is expected to be minimized. For example, natural
processes in the environment may degrade and eliminate natural
antioxidants, so that they do not then burden the environment. The
use of natural antioxidants is consistent with the approach of
using biodegradable surfactants, cosolvents, and solvents. An
example of a natural antioxidant is a flavonoid. Examples of
flavonoids are quercetin, glabridin, red clover, Isoflavin Beta (a
mixture of isoflavones available from Campinas of Sao Paulo,
Brazil). Other examples of natural antioxidants that can be used as
antioxidants in the present method of soil remediation include beta
carotene, ascorbic acid (vitamin C), and tocopherol (vitamin E) and
their isomers and derivatives. Non-naturally occurring
antioxidants, such as beta hydroxy toluene (BHT) and beta hydroxy
anisole (BHA) can also be used as antioxidants in the present
method of soil remediation.
[0067] For compounds that aerobically degrade, such as petroleum
hydrocarbons, oxygen, for example, in the form of a peroxide, can
be added with persulfate and Verusol to dissolve and chemically
oxidatively degrade petroleum hydrocarbons in the source area. The
oxygen contributed by the peroxides can then induce the
biodegradation by aerobic microorganisms of petroleum hydrocarbons
in the downgradient dissolved plume. Thermodynamically, aerobic
degradation reaction rates are much faster than anaerobic reaction
rates.
[0068] Compounds of incomplete oxidation of petroleum or
coal-derived materials from the S-ISCO.TM. process and naturally
aerobically degradable cosolvent/surfactant chemicals used in the
S-ISCO.TM. process, as well as their oxidation products, can be
biodegraded. Air, oxygen, solid peroxide compounds, and liquid
peroxide compounds can be added to enhance aerobic biodegradation.
However, traditional approaches are limited in that they only treat
the dissolved phase and do not treat the NAPL or organic liquid
phase. Certain contaminants can be difficult to biodegrade and
require complex biological systems difficult to sustain in the
subsurface. For example, certain PAH compounds require lignin
degrading white rot fungi to partially biologically degrade PAH
compounds to more readily degradable metabolites that are easier to
biodegrade (Zheng and Obbard (JEQ, 31:2002). Sorbed PAHs in soils
are not bioavailable and, therefore, not available to be
biodegraded in the aqueous phase (Guha and Jaffee (1996)). Yeom and
Ghosh (1998) concluded than mass transfer of PAHs from the sorbed
phase into the aqueous phase limited biodegradation rates of PAHs
and not biodegradation rate kinetics.
[0069] However, in the S-ISCO.TM. approach, the aerobically
biodegradable cosolvents and surfactants increase the rate of
solubilization of organics and NAPLs, and thereby greatly increase
the rate and potential efficiency of aerobic degradation of NAPLs.
For example, the S-ISCO.TM. process overcomes PAH mass transfer
limitations into the aqueous phase and simultaneously chemically
oxidizes the PAH compounds into either carbon dioxide and water or
more easily aerobically biodegradable compounds. Coupling VeruTEK's
S-ISCO.TM. process with oxygenation (by any of the means listed
above) for the treatment of NAPL source areas and downgradient
dissolved plumes is a significant enhancement over S-ISCO.TM. alone
or oxygenation for biodegradation alone. Depending on the amount of
NAPL compounds present and the ease with which the organic
compounds are biodegraded, either VeruSOL alone or with plume
oxygen addition can be used.
[0070] It can be important that the oxidant not react with the
surfactant so fast that the surfactant is consumed before the
surfactant can solubilize the contaminant. On the other hand, the
surfactant should not reside in the subsurface indefinitely, to
avoid being a contaminant itself. This degradation can be caused by
living organisms, such as bacterial, through a biodegradation
process. On the other hand, the surfactant can be selected to
slowly react with the oxidant, so that the oxidant survives
sufficiently long to solubilize the contaminant for the purpose of
enhancing its oxidation, but once the contaminant has been
oxidized, the surfactant itself is oxidized by the remaining
oxidant.
[0071] At the oxidation zone, it may be acceptable for the oxidant
to rapidly degrade the surfactant. If the surfactant is degraded,
oxidation of the contaminant may be slowed, because only a small
amount of contaminant is in the aqueous phase. However, at the same
time, the contaminant may be effectively immobilized. This
immobilization can prevent the contaminant from passing through the
oxidation zone. Thus, even if the oxidant rapidly degrades the
surfactant, the objective of preventing the contaminant from
spreading beyond the oxidation zone may still be achieved.
[0072] For example, aerobic microorganisms can metabolize and
consume excess oxidant, surfactant, cosolvent or another substance
introduced that migrates away from the locus where the primary
oxidant is injected. Thus, following a remediation procedure or
outside of a region where remediation is to take place, aerobic
microorganisms can reduce the amount or concentration of excess
oxidant, surfactant, cosolvent or another substance introduced
during the remediation process to a predetermined level, to ensure
that such an introduced substance is not itself viewed as a
contaminant. For example, a predetermined level of an introduced
substance can be a maximum amount of an introduced substance at a
site permitted by law or can be a maximum concentration of an
introduced substance permitted by law.
Reductive Zones
[0073] If a targeted contaminant contains a component degraded by
anaerobic microorganisms, a two region (or two zone) approach can
be developed. Near where the primary oxidant, for example, sodium
persulfate, is injected, the primary oxidant will induce an
oxidizing environment in the subsurface, and the primary oxidant
will oxidize or partially oxidize portions of this contaminant. In
this oxidizing environment, aerobic microorganisms can grow and
break down components of the contaminant susceptible to degradation
by aerobic microorganisms, such as non-halogenated aromatic
hydrocarbons. The primary oxidant, along with any oxygen naturally
present in the subsurface can be fully consumed in a reducing zone
away from where the primary oxidant is injected. If the oxygen
present is not fully consumed to form a reducing zone, a reducing
zone can be induced by injecting a chemical that consumes oxygen at
a point away from where the primary oxidant is injected. In this
reducing zone, anaerobic microorganisms can grow and break down
components of the contaminant susceptible to degradation by
anaerobic microorganisms, such as halogenated organics.
[0074] Thus, when anaerobic degradation pathways to further destroy
toxic organic chemical are preferred, the production of excess
aerobically degradable compounds can lead to depletion of dissolved
oxygen in the subsurface and create a low redox potential or
reducing environment favorable for anaerobic metabolism or
enzymatic reduction of organic and inorganic environmental
contaminants. Such low redox environments resulting from the use of
S-ISCO.TM. may result in inorganic reduction pathways associated
with common inorganic redox couples, that facilitate organic and
inorganic chemical reduction.
[0075] Anaerobic metabolism by anaerobic microorganisms can have
several different forms. Several of these anaerobic metabolic
processes, along with exemplary overall reactions and the redox
potential, E.sub.h, at which the processes can take place are
represented in the table below.
TABLE-US-00001 denitrification 2NO.sub.3.sup.- + 10e.sup.- +
12H.sup.+ .fwdarw. N.sub.2 + 6H.sub.2O 500~200 manganese IV
MnO.sub.2 + 2e.sup.- + 4H.sup.+ .fwdarw. Mn.sup.2+ + 2H.sub.2O
400~200 reduction iron III reduction Fe(OH).sub.3 + e.sup.- +
3H.sup.+ .fwdarw. Fe.sup.2+ + 3H.sub.2O 300~100 sulfate reduction
SO.sub.4.sup.2- + 8e.sup.- + 10 H.sup.+ .fwdarw. H.sub.2S +
4H.sub.2O 0~-150 fermentation 2CH.sub.2O .fwdarw. CO.sub.2 +
CH.sub.4 -150~-220
[0076] For example, manganese-reducing bacteria can use reduction
of manganese oxides to obtain energy. For example, iron-reducing
bacteria can use reduction of iron oxides to obtain energy. For
example, sulfideogenic bacteria (sulfate-reducing bacteria) can use
sulfate reduction to obtain energy.
[0077] For remediation of compounds that do not adequately
aerobically biodegrade, but do anaerobically degrade, peroxides are
not added. Anaerobic microorganisms can break down partially
oxidized contaminant that is a product of treatment of contaminant
with a primary oxidant such as sodium persulfate, for example, as
in the S-ISCO.TM. process. The growth and activity of such
anaerobic microorganisms is promoted by a reductive environment.
Such a reducing environment can be found, for example, in a region
removed from where the primary oxidant is injected. Partially
oxidized contaminant can move to a region with a reducing
environment, for example, by diffusion or by convection with
groundwater. The partially oxidized contaminant itself can consume
available oxygen to induce a reducing environment. Furthermore, the
partially oxidized hydrocarbon can serve as a food source for
anaerobic microorganisms. Alternatively, a microorganism organic
food source can be introduced to the subsurface. For example, the
microorganism organic food source can be introduced downgradient of
the point where the primary oxidant is introduced. For example, the
dissolved carbon (food for microorganisms) from VeruSOL, other
surfactants, or another substance consumes oxygen, can create an
anaerobic environment, and can create a reducing environment
enabling processes such as reductive dechlorination to take place.
Sulfate, for example, from persulfate, can be reduced biologically
so that the redox potential is lowered and reductive dechlorination
reactions can take place. Additionally, sulfate can be an
alternative electron acceptor to oxygen to enable anaerobic
degradation of some petroleum hydrocarbons, such as polycyclic
aromatic hydrocarbon (PAH) compounds, such as can be found at
manufactured gas plant sites.
[0078] Another condition at a site that can favor an approach using
bioremediation by anaerobic microorganisms is the presence of
chromium(+VI) (hexavalent chromium). Chromium(+VI) is soluble and
mobile in the subsurface and is very toxic. On the other hand
chromium(+III) is not very soluble and not very mobile in the
subsurface and is not very toxic. A reducing environment can reduce
the very hazardous chromium(+VI) to the much less hazardous
chromium(+III).
[0079] To induce a downgradient reductive environment, a food for
aerobic bacteria can be injected downgradient of the primary
oxidant. The aerobic bacteria can then be made to consume all of
the available oxygen to create a reductive environment.
[0080] For example, anaerobic microorganisms can metabolize and
consume excess surfactant, cosolvent or another substance
introduced that migrates away from the locus where it is injected.
Thus, following a remediation procedure or outside of a region
where remediation is to take place, anaerobic microorganisms can
reduce the amount or concentration of excess surfactant, cosolvent
or another substance introduced during the remediation process to a
predetermined level, to ensure that such an introduced substance is
not itself viewed as a contaminant. For example, a predetermined
level of an introduced substance can be a maximum amount of an
introduced substance at a site permitted by law or can be a maximum
concentration of an introduced substance permitted by law.
[0081] A reducing zone can be established, for example, by limiting
the amount of primary oxidant introduced, introducing a substance
that reacts with oxygen, or introducing food for microorganisms. A
substance that reacts with oxygen can include a zero-valent metal,
zero-valent iron, zero-valent manganese, zero-valent cobalt,
zero-valent palladium, zero-valent silver, and a particle of a
zero-valent metal coated with a polymer.
[0082] Herein, a "reductive zone" and a "reducing environment"
refer not only to a zone or environment in which the oxidation
potential is less than zero, but also to a zone or environment in
which the oxidation potential is equal to or greater than zero, but
less than an oxidation potential that is optimal for the growth and
metabolism of aerobic microorganisms. That is a "reductive zone"
and a "reducing environment" can favor certain anaerobic
microorganisms over aerobic microorganisms. In this text, it is
convenient to refer to "oxidative zones" and "reductive zones";
however, it is to be understood that there is in fact a continuum
of oxidative potentials at a site, for example, a subsurface, to be
or being remediated. Thus, in part of an "oxidative zone", only
aerobic microorganisms and no anaerobic microorganisms may be able
to proliferate and metabolize, while in another part of the
"oxidative zone", some anaerobic as well as aerobic microorganisms
may be able to proliferate and metabolize. In part of a "reductive
zone", only anaerobic microorganisms and no aerobic microorganisms
may be able to proliferate and metabolize, while in another part of
the "reductive zone", some aerobic as well as anaerobic
microorganisms may be able to proliferate and metabolize.
Use of Zero-Valent-Metal Particles
[0083] Zero valent metal particles can be used in controlling
aspects of a remediation process, such as in establishing oxidative
zones and/or reductive zones and controlling the rate at which
reactions occur in these zones.
[0084] For example, zero-valent iron (ZVI) can activate hydrogen
peroxide for pentachlorophenol (PCP) and methyl-tertiary-butyl
ether (MTBE) destruction. For example, powdered ZVI can activate
hydrogen peroxide and increase the rate and extent of compound
destruction. However, the rapid reaction rates of ZVI and the rapid
oxidation of ZVI with hydrogen peroxide may constraint the direct
application of uncoated ZVI particles as activators in subsurface
applications.
[0085] Nano-scale ZVI (zero-valent-iron) can be injected, e.g.,
into a subsurface, in an aqueous slurry. The ZVI can be mixed with
an organic guar material to provide structural integrity for
emplacement into fractures or permeable reactive barriers (PRBs).
The ZVI can be mixed with molasses or another type of biodegradable
substrate to promote physical, chemical, and/or biological
reduction processes, which can occur simultaneously. When organic
guar is used with ZVI, an enzyme can be added once the guar-ZVI has
been emplaced to induce biodegradation of the guar, thus exposing
the ZVI to contaminated groundwater.
[0086] In an embodiment, nano-scale (or larger-sized micro-sized
powdered) zero valent iron (ZVI) particles can be coated with thin
polymer films, and the coated ZVI particles can be introduced into
a subsurface to provide sustained activation of persulfate and
other oxidants for in situ chemical oxidation. The ZVI-polymer
combination can be referred to as "ZVIP" or, alternatively, "poly
ZVI." Such a polymer coating allows for control of the rate of
release of a metal activator so as to retain the activator in the
subsurface for as long as the oxidant is retained. Thus, the
polymer coating can prolong the activation and concentration of the
activator. As used herein, "zero valent" means an oxidation state
of zero, i.e., without charge. As used herein, "oxidant" includes,
for example, persulfate.
[0087] Polymers that can be used to coat the ZVI particles include,
for example, the biopolymers xanthan polysaccharide,
polyglucomannan polysaccharide, emulsan, alginate biopolymers,
hydroxypropyl methylcellulose, carboxy-methyl cellulose, ethyl
cellulose, chitin, chitosan, as well as, for example, the synthetic
polymers polymethyl methacrylate, polystyrene, and
polyurethane.
[0088] Other zero valent metals can be substituted for zero valent
iron (ZVI). For example, zero valent manganese (ZVMn) can be
substituted for zero valent iron in every embodiment discussed
herein, as can other transition metals, such as cobalt, palladium,
and silver. Furthermore, the zero valent metal, for example ZVI
and/or ZVMn, can be associated with additional metals, such as
palladium and cobalt, as well as other transition metals, for
example those that can activate persulfate or increase the
reactivity of ZVI, ZVMn, or another zero valent metal.
[0089] In an embodiment, nano- and micro-sized coated ZVI particles
can be used for sustained activation of Fenton chemistry and
persulfate in the destruction of organic and inorganic contaminants
in above- and below-ground remediation systems, water supply and
waste water treatment systems, as well as industrial applications
of Fenton's chemistry and activated persulfate, such as polymer
initiators. As used herein, "remediation" means the improvement of
the environmental quality of a location, whether such improvement
is necessitated by the conduct of humans or otherwise. Drinking
water treatment includes processing and treatment of surface and
subsurface water to supply potable water whether the systems are
large public water supply systems, individual home treatment units,
or for treatment of individual wells.
[0090] In an embodiment, Fenton chemistry and persulfate activated
with polymer coated ZVI particles is used to treat a wide range of
organic compounds in industrial wastewaters. For example, organic
compounds can include solvents, pesticides, herbicides,
polychlorinated biphenyls, dioxin, fuel oxygenates, manufactured
gas plants residuals, petroleum derived compounds, semivolatile
compounds, chlorinated organic compounds, halogenated organic
compounds, and other organic compounds. Polymer coated ZVI
particles can be used for sustained activation of Fenton Chemistry
and persulfate in industrial waste treatment systems. As used
herein, "nano-sized" and "nano-scale" mean particles less than
about 1 micron in diameter. As used herein, "micro-sized" and
"micro-scale" mean particles from about 1 to about 1000 microns in
diameter. As used herein, "macro-sized" and "macro-scale" mean
particles greater than about 1000 microns in diameter. In an
embodiment, permeable reactive barriers can be constructed that
contain mixtures of macro-, micro- and/or nano-sized PolyZVI
particles with other, more mobile reductants, and can be used for
remediation. As used herein, "reductants" includes the organic
compounds listed above as well as several inorganic compounds, such
as perchlorate, chromate, and arsenic. Examples of additional
reductants are molasses, vegetable oils, and other plant-based
organic chemicals, such as VeruSOL.
[0091] In an embodiment, the polymer coated ZVI or ZVMn particles
can be emulsified using various surfactants enabling: 1) less
reaction with subsurface materials and greater transport distance
in the subsurface, 2) mixing with other S-ISCO reagents during
preparation and injection into the subsurface, 3) coelution with
S-ISCO reagents such as cosolvents, surfactants, and oxidants or
any combination thereof, 4) intimate contact in micelles with
dissolved and emulsified NAPLs, better penetration into the
subsurface for use as a reduction technology, and 5) greater
compatibility and effectiveness for mixing ZVI and ZVMn with
surfactants and plant based biologically degradable amendments,
such as vegetable oils and molasses.
[0092] Polymer coated particles, such as polymer coated zero valent
metal particles, can be used with a surfactant or mixture of
cosolvents and surfactants to emulsify the polymer coated
particles. The particles, together with solubilizing or emulsifying
plant oils or other plant extracts can be injected into the
subsurface or spread on a ground surface to create a zone combining
physical, chemical, and/or biological processes, or any combination
thereof to reductively destroy or transform organic or inorganic
contaminants in the environment. The biological processes can
involve, for example, anaerobic organisms. As used herein,
"blending" includes, for example, emulsifying, solubilizing, or a
combination thereof.
[0093] As used herein, "reducing agent" includes, for example, zero
valent metal particles. As used herein, "half-life" means the time
required for one half of a process to be completed, for example the
time required for one half of a reagent to be consumed during a
reaction.
[0094] Nanoscale and microscale ZVI particles (and/or other zero
valent metal particles) can be injected into the subsurface to
create reduction zones by, for example: 1) creating a matrix in
which the ZVI is emplaced that allows transport of the ZVI into the
subsurface with a minimum amount of reaction of the ZVI particles
with, or adhesion of the ZVI particles to, the subsurface
mineralogy, for example, to prevent clogging and to promote
penetration of the ZVI particles through the subsurface soil;
and/or 2) adding a biological substrate such as molasses or
vegetable oil, which can provide a longer term biologically created
reduction zone than that achievable with nanoscale or microscale
ZVI alone.
[0095] A goal of in situ remediation using chemical oxidation is to
maximize the volume of soil treated for each injection well or
injection location. A factor affecting the volume of soil treated
is the longevity of the oxidant in the subsurface, given injection
flow rates, oxidant concentration, volume of injected fluid, mass
of oxidant added and the type of activation system used. When
activation is required, such as in the case of oxidants such as
persulfate and peroxide, the longevity of the activator should
ideally be close to that of the oxidant. To date, no activation
system has been demonstrated to have as long a life in the
subsurface as persulfate. Polymer coated ZVI (and/or other zero
valent metal) particles according to an aspect of the invention can
enable a more controlled time-release of the metal activator and/or
a more controlled rate of activation of oxidants such as persulfate
and peroxide than is possible with previously known metal-chelate
systems.
[0096] Zero valent metal particles can be used to activate an
oxidant, such as persulfate and/or hydrogen peroxide for in situ
chemical oxidation remediation. Nano- or larger-scale zero valent
metal (e.g., ZVI) material coated with, for example, partitioning
polymers, surfactant materials, or electrically conducting polymers
can be applied in the remediation of dense non-aqueous phase liquid
(DNAPL), light non-aqueous phase liquid (LNAPL), and other
contaminants and chemicals of concern.
[0097] Aspects of the invention also can be employed in contexts
other than treatment and remediation. For example, an aspect of the
invention can be utilized in the air purification, water supply,
and drug therapy fields. Production chemical and polymer activation
can be novel applications of coated Zero-Valent Iron (ZVI) and/or
other zero valent metals.
[0098] For example, polymer coating of macro-sized ZVI (and/or
other zero valent metal) particles, which can be used in permeable
reactive barriers (PRBs), can extend the life of these barriers,
e.g., by a factor or two or more. For example, resistant polymer
coatings can be added to the ZVI particles that can be removed by
some specialized chemistry, such as an acid or base rinse, chemical
stripping, thermal or electrical processes, or certain biological
processes. As used herein, "removing agent" means compounds or
other substances that possess the ability to remove the polymer
coating from a zero valent iron particle or other activator
particle. Mixtures of polymer coated ZVI particles with non-polymer
coated particles can be used in PRBs. For example, once non-coated
ZVI particles have been exhausted and are no longer able to
sufficiently reduce target contaminants (e.g., after a 20 year
life), then the polymer coated ZVI particles can be treated in situ
to remove the coatings and obtain a second 20 year period of PRB
life.
[0099] Polymer coated ZVI (and/or other zero valent metals) can be
used to create hydrophobic particles for remediation, for example
for DNAPL partitioning. ZVI particles can be coated with multiple
polymer layers. For example, the polymer layers can be of varying
polymer type and polymer layer thickness. A set of ZVI particles
having different thicknesses of polymer coating can be used in
remediation. The distribution of polymer coating thicknesses can be
tailored to control the rate at which the ZVI particles activate
oxidant or reduce contaminants and/or other compounds in the
environment at various times in the remediation process. One
purpose of a polymer coated ZVI can be to act as an activator of an
oxidant; in such an application it can be important that the
polymer coated ZVI remains capable of activating the oxidant for as
long as there is oxidant to be activated in the location. It can be
important that the activator is not consumed too rapidly. For
example, the polymer coating can limit the rate at which the
activator is exposed to the oxidant.
[0100] The activator should travel as far as the oxidant in the
location to be remediated. An uncoated activator may adhere to soil
particles, which would inhibit the activator's migration through
the location. By applying a polymer coating to the activator
surface, activator adherence to soil particles can be
minimized.
[0101] Altering the polarity and electrolytic conductivity of the
polymer can enable control of sorptive processes, including
potential partitioning into LNAPL and DNAPL mixtures. For example,
the following factors can be adjusted in applying poly-ZVI (and/or
polymer coated particles of other zero valent metals) to in situ
applications: (i) the type of polymer used, based on its reactivity
with an oxidant such as persulfate, biodegradation of by-products
and ability of ZVI to be coated; (ii) the thickness of the coating,
to control the rate at which the zero valent iron is exposed to
oxidants such as persulfate resulting in a controlled rate of free
radical production; (iii) the molecular size and other physical
properties of the polymer, to control penetration of the polymer
into the nano-scale ZVI; (iv) the electrolytic conductivity of the
coating, to avoid or induce sorption of the ZVIP onto various
mineral and organic materials, as appropriate for remediation
applications; and (v) the polarity of the polymer coating, to
control adsorptive and absorptive partitioning of the ZVIP with
natural organic carbon, bacterial mass, and/or LNAPL and DNAPL.
Design of Combined S-ISCO.TM. and Biodegradation Remediation
Processes
[0102] A method for determining a contaminant remediation protocol,
for example, of a protocol for remediating soil in a subsurface
contaminated with NAPL or other organic chemicals, can include the
following steps. Site soil samples can be collected under zero
headspace conditions (e.g., if volatile chemicals are present); for
example, samples representative of the most highly contaminated
soils can be collected. The samples can be homogenized for further
analysis. A target contaminant or target contaminants in the soil
can be identified. The demand of a sample of oxidant per unit soil
mass can be determined; for example, the demand of a soil sample
for a persulfate oxidant, such as sodium persulfate, can be
determined. An oxidant is, for example, a chemical or agent that
removes electrons from a compound or element, increases the valence
state of an element, or takes away hydrogen by the addition of
oxygen. A suitable oxidant and/or a suitable mixture of an oxidant
and an activator for oxidizing the target contaminant can be
selected. The oxidant can include an oxidant that generates a gas
phase upon its decomposition in the subsurface, the oxidant can be
added as a gas, or the oxidant can be added as a dissolved gas.
Further, in addition to the added oxidant, dissolved gas under
pressure can be added to the subsurface to generate a gas phase.
The behavior of the gas phase, in addition to the
cosolvent-surfactant mixture or surfactant alone, can lead to
enhanced extraction of the contaminant. Further, a dissolved gas
under pressure can be added to the subsurface to generate a gas
phase in addition to a cosolvent-surfactant mixture or surfactant,
which leads to enhanced extraction of the contaminant. Suitable
surfactants, mixtures of surfactants, and/or mixtures of
surfactants, cosolvents, and/or solvents capable of solubilizing
and/or desorbing the target contaminant or contaminants can be
identified; for example, suitable biodegradable surfactants can be
tested. Suitable solvents capable of solubilizing and/or desorbing
the target contaminant or contaminants can be identified; for
example, suitable biodegradable solvents such as d-limonene can be
tested. Various concentrations of cosolvent-surfactant mixtures or
surfactants alone can be added to water or groundwater from a site
along with controlled quantities of NAPLs. Relationships of the
extent of dissolution of the NAPL compounds with the varying
concentrations of the cosolvent-surfactant mixtures or surfactants
can be established by measuring the concentrations of the NAPL
compounds that enter the aqueous phase. Relationships between the
interfacial tension and solubilized NAPL compounds and their
molecular properties, such as the octanol-water partition
coefficient (K.sub.ow) can also be established that enable optimal
design of the dissolution portion of the S-ISCO process. Various
concentrations of cosolvent-surfactant mixtures or surfactants
alone can be added to water or groundwater from a site along with
controlled quantities of contaminated soils from the site.
Relationships of the extent of solubilization of the sorbed COC
compounds with the varying concentrations of the
cosolvent-surfactant mixtures or surfactants can be established by
measuring the concentrations of the sorbed COCs that enter the
aqueous phase. Relationships between the interfacial tension and
desorbed and solubilized compounds and their molecular properties,
such as the octanol water partition coefficient (K.sub.ow), can
also be established that enable optimal design of the dissolution
portion of the S-ISCO process. The simultaneous use of oxidants and
surfactants or cosolvent-surfactant mixtures in decontaminating
soil can be tested. For example, the effect of the oxidant on the
solubilization characteristics of the surfactant can be evaluated,
to ensure that the oxidant and surfactant can function together to
solubilize and oxidize the contaminant. The quantity of surfactant
for injection into the subsurface can be chosen to form a Winsor I
system or a microemulsion.
[0103] For example, the type and quantity of surfactants and
optionally of cosolvent required to solubilize the target
contaminant can be determined in a batch experiment.
[0104] The spatial concentration distribution of the target
contaminant can be determined. A hydrogeological property of the
subsurface can be determined. The determined spatial concentration
distribution of the target contaminant and the hydrogeological
property can be used to determine a target depth for the oxidant,
gas phase generating oxidant, or pressurized dissolved gas in
liquid, cosolvent-surfactant or surfactant and injection site(s) of
the above injectants, and an extraction site for the
contaminant.
[0105] Experimentation on the effects of various oxidants,
combinations of oxidants, and activators on the stability and
activity of cosolvent-surfactant mixtures and surfactants can be
readily conducted to provide information to optimize S-ISCO
treatment conditions. Testing of the sorption or reaction of the
surfactant or surfactant-cosolvent mixture can be conducted to
determine the transport and fate properties of the surfactant or
surfactant-cosolvent mixture in soils, rock and groundwater.
Testing can be conducted in batch aqueous or soil slurry tests in
which individual cosolvent-surfactant mixtures or surfactants at
specified initial concentrations are mixed together with individual
oxidants or mixtures of oxidants and activators. The duration of
the tests can be a minimum of 10 days and as long as 120 days,
dependent on the stability of the oxidant-surfactant system needed
for a particular application.
[0106] Testing of oxidants, surfactants, activators, cosolvents,
and/or solvents can be conducted with the contaminant in the
non-aqueous phase and/or sorbed phase in aqueous solution, or with
the contaminant in a soil slurry or soil column. A soil slurry or
soil column can use a standard soil or actual soil from a
contaminated site. An actual soil can be homogenized for use in a
soil slurry or soil column. Alternatively, an intact soil core
obtained from a contaminated site can be used in closely simulating
the effect of introduction of oxidant, surfactant, and/or solvent
for treatment.
[0107] The microorganism population in a site to be remediated, for
example, a subsurface, can be characterized. For example, a
technique such as metagenomic analysis or another technique can be
used to determine the types and density (e.g., number per unit
subsurface volume) of aerobic and/or anaerobic microorganisms at
one or more locations in a site to be remediated. For example,
resident microorganisms such as bacteria, fungi, molds, yeasts,
archaea, protists, algae, plankton, microscopic plants, protozoans,
lichens, microscopic animals, planaria, and amoebas can be
identified. Maps of the site to be remediated that present
concentrations of different microorganisms can be developed and can
be used in the development of a remediation process. Microorganisms
that are desirable, for example, because they biodegrade
contaminants or partially oxidized products of contaminants and/or
because they biodegrade excess oxidant, surfactant, and/or
cosolvent, can be identified. Conditions which cause such desirable
microorganisms to proliferate and/or increase the metabolic rate of
such desirable microorganisms can be identified either through
applying prior knowledge or conducting experiments. Microorganisms
not present in the site to be remediated, but would be desirable if
present can be identified, and protocols for seeding the site to be
remediated with such desirable microorganisms can be developed.
[0108] The effect of oxidants, surfactants, activators, cosolvents,
and/or solvents to be used in the remediation process on aerobic
and anaerobic microorganisms can be tested. The selection of
substances such as oxidants, surfactants, activators, cosolvents,
and/or solvents for the remediation process can be indicated by the
tendency of a substance, alone or in conjunction with another
substance, to promote the proliferation and/or metabolism of
desirable microorganisms and/or to suppress the proliferation
and/or metabolism of undesirable microorganisms. The selection of a
substance can be contraindicated by its tendency to promote the
proliferation and/or metabolism of undesirable microorganisms
and/or to suppress the proliferation and/or metabolism of desirable
microorganisms. Such testing can indicate the introduction of
additional substances to the site to be remediated for the purpose
of promoting the proliferation and/or metabolism of desirable
microorganisms and/or suppressing the proliferation and/or
metabolism of undesirable microorganisms. For example, such testing
can indicate that nutrients for desirable microorganisms be added,
that acid, base, and or buffer be added to establish and maintain
an optimal pH for desirable microorganisms, and/or that an oxidant
or reductant be added to a particular region of the site to be
remediated, for example, to establish an oxidative or reductive
zone.
Monitoring and Control of Combined S-ISCO.TM. and Biodegradation
Remediation Processes
[0109] Before, during, and after the injection of injection fluid
and the removal of contaminant, the subsurface can be monitored to
ensure that the remediation process is proceeding
satisfactorily.
[0110] A method can include monitoring the concentration and/or
spatial distribution of quantities such as contaminant, products of
partial oxidation of contaminant, oxidant, reductant, surfactant,
cosolvent, and/or aerobic and/or anaerobic microorganisms in a site
being remediated, such as a subsurface. Examples of other
quantities that can be monitored include pH, oxidation potential,
temperature, pressure, salinity, and concentration of other
substances. Monitoring can be conducted at one or several locations
within the site being remediated. The monitoring date can be used
to monitor the progress of the remediation, for example, reduction
in the concentration of contaminant. The monitoring data can be
used to detect, for the purpose of suppressing, undesired
conditions, such as the migration of contaminant off of a site
being remediated. The monitoring data can be used in determining
how to achieve goals of the remediation, for example, speedy
destruction of a contaminant without mobilization of the
contaminant off of a site. For example, the monitoring data may
indicate that the introduction of substances such as oxidants,
reductants, surfactants, activators, cosolvents, solvents,
nutrients, and/or seeded microorganisms indicated (or
contraindicated) during the design phase of a project be stopped or
started. For example, the monitoring data may indicate that
parameters such as concentration and/or flow rate of an injected
substance and/or vacuum imposed on an extraction well be changed.
The monitoring data can be provided to a control system that can
automatically adjust parameters of the remediation process.
[0111] For example, the concentration and/or spatial distribution
of hydrogen peroxide, another oxidant, a surfactant, and/or a
cosolvent that have been injected into the subsurface can be
monitored continuously, periodically, or sporadically, for example,
to ensure that the hydrogen peroxide, another oxidant, a
surfactant, and/or a cosolvent are being transported to regions of
the subsurface where they can promote the oxidation of contaminant
and mobilization of contaminant to an extraction well. For example,
the concentration and/or spatial distribution of the contaminant,
one or more components of the contaminant, the product of
contaminant oxidation, and/or one or more components of the product
of contaminant oxidation can be monitored continuously,
periodically, or sporadically. For example, such monitoring can
ensure that the contaminant is being destroyed by oxidation,
modified by oxidation, so that it is more susceptible to
degradation, e.g., by a chemical or microbial process, being
mobilized to an extraction well, and/or not being mobilized to a
region in which the contaminant can have a more deleterious impact,
e.g., below a residential area, than the region where the
contaminant was located prior to starting remediation.
EXAMPLES
Example 1
[0112] A method for reducing the concentration of a contaminant in
a soil includes the following. An oxidant and a surfactant can be
introduced into a subsurface containing the soil. The surfactant
can solubilize and/or desorb the contaminant. The oxidant can
oxidize the solubilized contaminant in the subsurface, so that the
amount of the contaminant in the soil is substantially reduced. A
microorganism in the subsurface can biodegrade the contaminant
and/or products of oxidation of the contaminant. The overall rate
of oxidization of the contaminant can be controlled to a
predetermined value and the overall rate of solubilization of the
contaminant can be controlled to a predetermined value by selecting
the oxidant, surfactant, and antioxidant and adjusting the
concentrations of surfactants, oxidants, and antioxidants, so that
the rate of oxidation of the contaminant is greater than, less
than, or equal to the rate of solubilization of the contaminant in
accordance with a predetermined decision.
Example 2
[0113] In an embodiment, a composition includes soil, a non-aqueous
phase contaminant, a quantity of surfactant, an oxidant, and a
microorganism. The quantity of surfactant can be sufficient to
solubilize the nonaqueous phase liquid contaminant. The surfactant
can form a Windsor I solution or microemulsion. The microorganism
can biodegrade the contaminant and/or products of oxidation of the
contaminant.
Example 3
[0114] In an embodiment, a treated composition includes soil, an
oxidized contaminant, and an oxidant residue. The treated
composition can further include a microorganism.
Example 4
[0115] A method for reducing the concentration of a contaminant in
soil can include solubilizing the contaminant and oxidizing the
contaminant. Mobilization of the contaminant during solubilization
and oxidation can be minimal. The method can further include using
a microorganism to biodegrade the contaminant and/or products of
oxidation of the contaminant.
Example 5
[0116] A method for reducing the concentration of a contaminant in
soil can include locally mobilizing the contaminant and oxidizing
the contaminant. The method can further include using a
microorganism to biodegrade the contaminant and/or products of
oxidation of the contaminant.
Example 6
[0117] A method for determining a subsurface contaminant
remediation protocol can include the following. A soil sample can
be collected from the subsurface. At least one target contaminant
for concentration reduction can be identified. A surfactant and/or
a cosolvent can be chosen for injection into the subsurface to
solubilize the at least one target contaminant. An oxidant and
optionally an activator for the oxidant can be chosen for injection
into the subsurface to oxidize the target contaminant. A quantity
of surfactant can be chosen for injection into the subsurface to
form a Winsor I system or a submicellar surfactant solution or a
microemulsion. A microorganism or class of microorganisms can be
selected to biodegrade the identified contaminant and/or products
of oxidation of the identified contaminant.
Example 7
[0118] A method for determining a subsurface contaminant
remediation protocol can include the following. A soil sample from
the subsurface can be collected. At least one target contaminant
for concentration reduction can be identified. A surfactant or
surfactants and/or a solvent can be chosen for injection into the
subsurface to desorb and solubilize the at least one target
contaminant. An oxidant and optionally an activator can be chosen
for injection into the subsurface to oxidize the target
contaminant. A quantity of surfactant for injection into the
subsurface to form a Winsor I system or a microemulsion can be
chosen. The spatial concentration distribution of the target
contaminant can be chosen. A hydrogeological property of the
subsurface can be determined. The determined spatial concentration
distribution of the target contaminant and the hydrogeological
property can be used to determine the target depth for the
surfactant and oxidant and optionally for the solvent and
activator. A microorganism or class of microorganisms can be
selected to biodegrade the identified contaminant and/or products
of oxidation of the identified contaminant.
Example 8
[0119] A method for reducing the concentration of a contaminant in
a soil at a target depth can include the following. A target depth
range for reducing the concentration of the contaminant can be
identified. A surfactant, an oxidant, and optionally a non-oxidant,
non-activator salt can be selected. The surfactant, the oxidant,
and optionally the non-oxidant, non-activator salt can be
introduced into a subsurface containing the soil. The surfactant
can solubilize and/or desorb the contaminant. The oxidant can
oxidize the contaminant in the subsurface, so that the
concentration of the contaminant in the soil is substantially
reduced. A microorganism or class of microorganisms can be selected
to biodegrade the identified contaminant and/or products of
oxidation of the identified contaminant. The surfactant and the
oxidant can be introduced together and the oxidant can be selected
so that the combination of the surfactant and the oxidant has a
density to maximize the fraction of the surfactant and oxidant
mixture that remains within the target depth range. The
non-oxidant, non-activator salt can be introduced together with the
surfactant, the oxidant, or both, and the non-oxidant,
non-activator salt can be selected so that the mixture of the
non-oxidant, non-activator salt with the surfactant, the oxidant,
or both has a density to maximize the fraction of the surfactant
and maximize the fraction of the oxidant that remains within the
target depth range.
Example 9
[0120] A method for reducing the initial mass of a contaminant in a
volume of soil can include the following. A volume of a solution
including an oxidant and a volume of a solution including a
surfactant can be introduced into a substrate containing the soil.
A microorganism or class of microorganisms can be selected to
biodegrade the identified contaminant and/or products of oxidation
of the contaminant. At least 40% of the initial mass of contaminant
can be eliminated from the volume of soil. In an embodiment, no
more than 5% of the combined volume of the solution including the
oxidant and the volume of the solution including the surfactant is
extracted from the soil.
Example 10
[0121] A method for reducing the concentration of a contaminant in
a soil can include the following. An oxidant and a surfactant can
be introduced into a ground surface or above-ground formation,
structure, or container containing the soil. The surfactant can
solubilize and/or desorb the contaminant. The oxidant can oxidize
the solubilized contaminant, so that the amount of the contaminant
in the soil is substantially reduced. A microorganism or class of
microorganisms can be selected to biodegrade the identified
contaminant and/or products of oxidation of the contaminant. The
overall rate of oxidization of the contaminant can be controlled to
a predetermined value and the overall rate of solubilization of the
contaminant can be controlled to a predetermined value by selecting
the oxidant, surfactant, and antioxidant and adjusting the
concentrations of surfactants, oxidants, and antioxidants, so that
the rate of oxidation of the contaminant is greater than, less
than, or equal to the rate of solubilization of the contaminant in
accordance with a predetermined decision.
Example 11
Remediation of Chlorinated Solvent
[0122] An embodiment of the invention is the simultaneous or
sequential use of cosolvent-surfactant mixtures, for example,
Citrus Burst 3 with activated persulfate (activated at a high pH
with NaOH) for the treatment of sites contaminated with chlorinated
solvents and other chlorinated or halogenated compounds.
[0123] In order to test the treatment of chlorinated compounds, a
chlorinated solvent DNAPL was obtained from a site consisting of
chlorinated solvents and chlorinated semi-volatile compounds.
Composition of the chlorinated solvent DNAPL is presented based on
determinations using USEPA Methods 8260 and 8270. An aliquot of the
DNAPL was mixed with a suitable quantity of deionized water to
determine the equilibrium solubility of the individual compounds in
the presence of the DNAPL. Experimental conditions for these
dissolution tests are reported in Table 2.
TABLE-US-00002 TABLE 2 Experimental Conditions for Chlorinated
DNAPL Dissolution Experiments Water Citrus Citrus Exp. g DNAPL
Burst-3 Burst-3 DNAPL.sub.max NaCl NaCl No. Total g g g/L g/L g g/L
1 60 2 0.05 0.8 33.3 3 50 2 60 2 0.1 1.7 33.3 3 50 3 60 2 0.25 4.2
33.3 3 50 4 60 2 0.5 8.3 33.3 3 50 5 60 2 1 16.7 33.3 3 50 6 60 2
2.5 41.7 33.3 3 50 7 60 2 5 83.3 33.3 3 50 8 60 2 0 0.0 33.3 3 50 9
60 2 0 0.0 33.3 3 50
[0124] The data collected under the experimentation conditions
presented in Table 2 were obtained at 25.degree. C. with 60 rpm
shaker table mixing for 48 hours. After the shaker was shut off,
the samples sat quietly for 5 minutes before the supernatant was
analyzed. DNAPL.sub.max represents the maximum concentration of
DNAPL that may dissolve, given the mass of DNAPL and the volume of
water.
[0125] Results of these analyses and the pure compound solubilities
of the individual compounds are reported in Table 3.
TABLE-US-00003 TABLE 3 Chlorinated DNAPL Composition and
Dissolution in Control Sample Without Cosolvent-Surfactant Observed
Pure Compound Solubility in Aqueous DNAPL Control Sample DNAPL
Solubility Compound Composition % (mg/L) Mol Fraction (mg/L)
Tetrachloroethene (PCE) 67.68% 140 0.194 800 Carbon Tetrachloride
(CTC) 19.65% 100 0.724 129 Hexachlorobutadiene (HCBD) 4.15% NA
0.006 0.005 Hexachlorobenzene (HCB) 0.93% 1.4 0.024 3.2
Hexachloroethane (HCE) 7.42% NA 0.051 50 Octachlorostyrene (OCS)
0.16% NA 0.000 insoluble Octachloronaphthalene (OCN) 0.01% NA 0.001
insoluble
[0126] Carbon tetrachloride and tetrachloroethylene comprised more
than 87 percent of the DNAPL. Being a saturated compound, carbon
tetrachloride is generally a pervasive and difficult to degrade
compound once introduced to the subsurface. The observed
solubilities of the DNAPL compounds in the aqueous phase are quite
low and will be the basis to compare enhanced dissolution using
Citrus Burst-3. After 48 hours of slowly mixing the DNAPL and water
mixtures, the samples were allowed to sit for 5 minutes and then
samples of the solubilized fraction of the mixture were collected
and analyzed for VOCs using USEPA Method 8260. Samples from
experiment number 1, 3, 5, 7, and 8 (control) were analyzed.
Additionally, measurements of interfacial tension (IFT) were
conducted on the samples after the 48-hour period.
[0127] Once the concentrations of the VOC compounds in the
solubilized phase were measured, the solubility enhancement
factors, .beta., was calculated for each compound at each Citrus
Burst concentration. .beta. is the ratio of the concentration in
mg/L of the individual VOC compound dissolved with the CB-3 divided
by the solubility of the same individual VOC compound dissolved in
the presence of the DNAPL without the cosolvent surfactant. The
results of this test are found in FIG. 6. The .beta. values varied
from a low of 2.79 for carbon tetrachloride at a Citrus Burst
concentration of 0.8 g/L, to a high of 857.14 for
hexachlorobutadiene at a Citrus Burst concentration of 83.3 g/L. A
log-normal plot of the total VOCs dissolved using various doses of
Citrus-Burst 3 versus the interfacial tension measurement (IFT)
taken in each vial after 48 hours of contact can be found in FIG.
7. For example, it can be readily observed from FIG. 6 that IFT
measurements can be used to easily determine the solubility
potential of the cosolvent-surfactant mixture. The highly linear
log-normal relationship of the logarithm of the octanol-water
partition coefficient (log(K.sub.ow)) and the solubility
enhancement factor, .beta., for each of the tested Citrus Burst-3
concentrations allows prediction of the solubility behavior of many
organic compounds using the relationship. These types of
experiments and relationships can be used to screen and determine
optimal types and concentrations of surfactants and
cosolvent-surfactant mixtures that can be used to optimize
dissolution of NAPL organic compounds useful in the S-ISCO
process.
[0128] Aliquots of the Citrus Burst-3 enhanced solubilized DNAPL
mixtures were added to aliquots of a sodium persulfate solution and
the bulk solution pH adjusted to greater than 12 using NaOH. Prior
to adding the sodium persulfate, initial VOC and SVOC
concentrations of the solutions were determined using USEPA
Methods, 8260 and 8270, respectively, as shown in Table 3. These
solutions were slowly mixed at 60 rpm on an orbital shaker table
for 14 days. After the 14 day mixing period the solutions were
removed from the mixer and the VOC and SVOC concentrations were
measured using USEPA Methods 8260 and 8270. The overall removal of
VOCs and SVOCs was calculated for each treatment condition and the
results can be found in FIG. 8. The T1 and T3 samples, which
initially had 0.8 g/L and 4.3 g/L, respectively of Citrus-Burst 3,
had greater than 99 percent removals of VOCs and SVOCs after 14
days of treatment. The T7 sample that initially had a Citrus
Burst-3 concentration 83.3 g/L and a much greater concentration of
VOCs and SVOCs than the other vials, removed of VOCs and SVOCs were
94 percent and 76 percent, respectively. The initial IFT
measurements for the T1, T3, and T7 tests prior to oxidation were
63.9 mN/m, 48.5 mN/m and 35.40 mN/m, respectively. Following the 14
day oxidation period, the final IFT readings for the T1, T3, and T7
tests were 74.4 mN/m, 73.1 mN/m and 35.40 mN/m, respectively. The
alkaline persulfate substantially removed the dissolved VOCs and
SVOCs from the T1 and T3 samples, as well as returning the IFT
values to background conditions of water without any added
cosolvent-surfactant. In the case of the T7 sample, the IFT values
remained low while high removal percentages of the VOCs and SVOCs
were observed. It is likely that additional time was required to
destroy the remaining VOCs and SVOCs in the T7 vial and to increase
the IFT to background conditions. Digital photographs were taken of
the test vials before, during and after the 14 day treatment. It
was evident after 14 days of treatment that the turbidity and red
color (associated with the Suidan IV dyed DNAPL) were completely
removed and the solutions returned to a clear condition. In the T7
sample, the red color was removed (indicative of most of the
dissolved DNAPL removed) and much of the turbidity was reduced.
[0129] Additional tests that can be performed include the ability
of various microorganisms to biodegrade the chlorinated
hydrocarbons and/or partially oxidized products of the chlorinated
hydrocarbons. Further, tests can be performed on how to optimize
conditions such as pH and oxidation potential to promote the
proliferation and metabolism of microorganisms that can perform
such biodegradation.
[0130] The embodiments illustrated and discussed in this
specification are intended only to teach those skilled in the art
the best way known to the inventors to make and use the invention.
Nothing in this specification should be considered as limiting the
scope of the present invention. All examples presented are
representative and non-limiting. The above-described embodiments of
the invention may be modified or varied, without departing from the
invention, as appreciated by those skilled in the art in light of
the above teachings. It is therefore to be understood that, within
the scope of the claims and their equivalents, the invention may be
practiced otherwise than as specifically described.
* * * * *